In the third season opener, Hardcastle and McCormick go on a photo exhibition with Buzz Bird, one of the judge's old friends. To their regret, Buzz, who is a pilot, has a heart attack while flying them over a stretch of Oregon wilderness. While Hardcastle and McCormick survive the crash landing, they are stranded miles from civilization and unknowingly attract the attention of Taylor Walsh, a mountain "pirate" who has made his living by robbing tourists. After suffering through a horrible rain storm, Hardcastle decides to tell Mark how much he appreciates their friendship. Although Mark pretends to be asleep, he actually hears everything the judge has to say. The next day, the two men come across the dead body of a murdered man. Realizing that they are being tracked, they decide to speed up their journey by white water rafting. Once the two men are in the water, Taylor and his men attack. Fleeing to land, Hardcastle and McCormick manage to evade the pirates. Turning the tables, the two men capture Taylor and his men. A month later, the judge and Mark, with their prisoners in tow, finally return to civilization.

After race car driver Kiki Cutter is injured during a race, Mark, knowing her from his own racing days, decides to pay her a visit. Fortunately for Kiki, Mark arrives just as someone tries to kill her. Although the killer manages to escape, Mark does manage to get his license plate number. Believing that the attempted assassination may be tied into Kiki's crash, Mark sneaks a look at the car. Confirming his suspicions, Mark finds evidence that Kiki's car was sabotaged. Meanwhile, Hardcastle traces the assassin's license plate to Hal Jenkins, an insurance broker. Some of the pieces of the puzzle are tied together when a recovering Kiki reveals that she has been secretly planning on divorcing Sammy "Sidewinder" O'Connell, her race driver husband. Once, Hardcastle has stopped Jake Thomas, the man who tried to kill Kiki, as well as arrested Jenkins, Mark, with some financial backing from the judge, decides to challenge O'Connell in a major car race. Thanks to his superior driving skills, Mark defeats O'Connell and settles a longstanding rivalry between them. Afterwards, O'Connell, who had selfishly acted out of fear of how the divorce would impact his career, is arrested for his part in the attempts on his wife's life.

When Bill Bauer is declared dead after being MIA from the Marines for 10 years, Mark, the soldier's former best friend, is asked to handle the funeral arrangements. The funeral does have one positive result for it reunites Mark with old friends Patrick Burke, Jeff Steffan and Peter Trigg. To Mark's surprise, shortly after the funeral, Bauer turns up very much alive. Upon being confronted by his angered friend, Bauer explains that he had been in charge of destroying cash when the United States pulled out of Vietnam in 1975. Instead of following orders, however, he had waited for an opportunity to smuggle the money into the country. Continuing, Bauer relays how he used "his" casket as a way of transporting the cash. Bauer realizes that his plan is falling apart when someone tries to kill him. Seeing no alternative, Bauer decides to go after the men chasing him. Following Bauer, Hardcastle and McCormick discover that Peter Trigg, secretly the leader of a group of terrorists, is trying to get a hold of Bauer's money in order to buy weapons. Although Trigg temporarily manages to capture Hardcastle and McCormick, the two men are able to turn the tables thanks to Bauer's intervention. Later, the police are all set to take Bauer into custody when the ex-soldier decides to disappear again.

Although Hardcastle is initially pleased to be invited to a party on a private train, his emotion changes to anger when he discovers that he has been lured onto the train under false pretenses. His ire is further raised upon discovering that the train is not scheduled to stop for another day. One small consolation: Mark, accidentally trapped on board the train, is around to help him find out what is going on with the trip. The mystery takes a deadly turn when one of the passengers is murdered. Although the unknown murderer temporarily manages to get rid of Mark by throwing him off the train, the ex-race car driver, who is unable to identify his assailant, pools his resources and returns to the train down the track. Another murder prompts Hardcastle to set a trap for the killer. While Hardcastle pretends to be a victim, Mark purposely lets slip that the judge had obtained evidence against the killer. Taking the bait, passenger Carl Sharples tries to search Hardcastle's "body". Exposed as the killer, Carl reveals that he has been eliminating the people (strict teacher, ex-girlfriend, army commander, high school coach, that he selfishly believes "ruined" his life. With Mark's help, Hardcastle stops Carl before he can hurt anyone else.

On vacation, Hardcastle travels down to Canary Creek, California to participate in an annual fishing contest. To Hardcastle's surprise, Tina Cutter, the local sheriff's sixteen year old daughter, accuses him of rape. While transporting the judge to jail, Sheriff Dale Cutler tries to kill him. Thanks to Mark's timely arrival, the sheriff is forced to postpone his assassination. Realizing that the judge is in mortal danger, Mark, posing as a drunk, breaks his friend out of jail. Once free, Hardcastle begins to question why Tina framed him. Recalling an earlier meeting with the sheriff, Hardcastle, who has concluded that Tina's own father set up the false rape, realizes that he had mentioned a plane he came across while fishing. Returning to the fishing site, Hardcastle seeing the sheriff and some of the local residents dismantling the plane, ascertains that the sheriff had discovered a downed drug transport. Following the sheriff, Hardcastle and McCormick watch as the residents try to sell the drugs to a major dealer. With the help of a conveniently located forklift, Hardcastle and McCormick manage to capture the sheriff and the dealers. Later, once the sheriff's plans have been exposed, Hardcastle is cleared of the rape charges.

Entering the hospital for a routine checkup, Hardcastle discovers that he is dying from an incurable disease. Not wanting to let his friend just fade away, Mark convinces Hardcastle to live his remaining days to the fullest, Taking Mark's advice to heart, the judge, using the money he inherited from his wife, buys a one million dollar boat. Hardcastle's boating career is short lived, however, for armed men steal the boat. Although Hardcastle is initially willing to let the police handle the crime, he changes his mind after discovering that the hospital made a mistake and he is not really dying. Searching the docks, Hardcastle and McCormick locate the boat. Instead of reclaiming his property, Hardcastle discovers that the boat really belongs to an influential Senator. Realizing that Barry Jackson, the man who illegally "sold" him the boat, is a con artist, Hardcastle contacts his bank to find out where his money is being transferred. With Lieutenant Harper's help, Hardcastle and McCormick stake out the bank and capture Jackson. In the process, Hardcastle recovers his money.

Mark surprises the judge when he not only qualifies for, but becomes a winner on, The 1 Million Dollar Trivia Master, a television game show. Unbeknownst to Mark, veteran game show producers Harry Baxter and Art Healy, envisioning big ratings, decide to help the ex-race car driver along once they discover that the audience is cheering for him to succeed. To guarantee a winning streak, the producers have Hardcastle's estate bugged and begin basing their questions on Mark's home practice sessions. Although Hardcastle quickly realizes that something is amiss, Mark is unwilling to accept that the game is rigged. After Diane Templeton, one of the trivia show's employees, dies under mysterious circumstances, Mark turns around and admits that something is seriously wrong. Searching the show's offices, Hardcastle finds out why Diane was killed: She had obtained a tape proving the show is fixed. Meanwhile, Baxter and Healy discover that Bryce Benson, the shows host, had taken their plan to a deadly conclusion by killing Diane. Not wanting to face murder charges, the producers decide to tell Hardcastle everything. During the taping of the show's final round, Mark, giving up his chance to be a big winner, reluctantly helps the police stop Benson. Hinting at the series eventual conclusion, Mark jokes about going to law school in this episode.

Shortly after contacting her friend Mark for help, wrestler Kate Murphy dies during a match. Recognizing that Kate's death was no accident, Mark decides to follow-up on his friend's suspicions that wrestling promoter Marty Torrance is behind the disappearance of a number of young woman. Upon assembling a plan of action, Hardcastle asks friends Lucy and Denise to go undercover as wrestlers. Posing as a wrestling promoter, Hardcastle has Denise, using the alias of "White Lighting" challenge Nancy Mack, one of Marty's wrestlers. Impressed with Denise's ability, Marty agrees to a match and allows Hardcastle's team to train in his gym. Furthermore, Marty, seeing potential in Lucy, asks the "wrestler" out on the date. Although Lucy only goes on the date to get evidence against Marty, the promoter has his own plans. Before Lucy is able to contact the judge, however, Marty prepares to sell her to a white slavery ring. Worried about Lucy, Hardcastle confronts Nancy. Having suffered a falling out with Marty, Nancy comes clean and tells the judge about Marty's plans. Searching the promoter's house, Hardcastle and McCormick come across the location of Marty's meeting with the slavers. Thanks to Mark's driving expertise, Hardcastle arrives at the meeting site in time to rescue Lucy and stop the slavers.

While judging the Miss Sixteen beauty contest, Hardcastle becomes wrapped up in the life of car salesman Ed Whitman, the pageants grand marshal. Worried when her boyfriend Victor Hernandez reveals that his uncle disappeared while sneaking across the Mexican-United States border, Melissa Whitman, Ed's sixteen year old daughter and one of the pageant's contestants, goes to Hardcastle for help. Although Victor's uncle does eventually turn up alive, Hardcastle decides to find out what happened. With Victor's reluctant help, Hardcastle discovers that a man was murdered during a transfer of illegal immigrants across the border. Thanks to Victor, Hardcastle also learns that a lawyer named Antonio Morales, who claims no knowledge of the murder, has been helping to arrange illegal immigrations. Before the judge can get more information from Victor's uncle, the illegal immigrant is murdered. With Morales' help, Hardcastle goes undercover as a perspective immigrant. The judge's plan works and the illegal immigration ring is stopped. At the same time, Hardcastle discovers that Ed Whitman is the mastermind behind the illegal operation. Returning to the United States, Hardcastle and McCormick help the police take Whitman into custody. As the episode ends, Melissa loses the pageant to a girl named Sara Jane Rose.

Innocently given a friendly kiss by a woman named Aleeya "Ali" Casir, Mark unwittingly falls into the middle of a major international incident: Assuming that Mark is the American his daughter has been living with, Sheik Abdullah Casir, Ali's father and the leader of an oil rich mid-eastern country, decides to take whatever steps are necessary to protect his son's honor. As a result, Casir orders his Americanized daughter to marry Mark. Meanwhile, Hassan and Rabin, Casir's sons, begin to set up a drug dealing operation. Hoping to maintain friendly relations with Casir, the State department approaches Mark and "requests" that he marry Ali. Although Hardcastle tries to explain to Casir that Biff Anderson, Ali's real boyfriend, would be more than willing to take Mark's place, Casir, having already made an official announcement, is unwilling to change his plans. Forced to follow through with the wedding, Hardcastle, having learned about Casir's drug dealing sons, decides to use the ceremony as an opportunity to expose Hassan and Rabin. Confronted with his sons' guilt, an angered Casir vows to spare himself grief by staying out of his children's lives. As such, the wedding is canceled. Later, Mark is amused to hear that Ali has left Biff to marry a 35 year old television executive.

In an unusual coincidence, a judge's convention is scheduled at the same hotel as a major mob meeting. Unable to do anything about the mobsters (as they have not been caught breaking any laws), Hardcastle instead concentrates on his nomination for a lifetime achievement award. For some extra insurance, Hardcastle pulls strings and has himself put in what he considers to be a lucky room. Actually, Hardcastle ends up in a room originally assigned to a hitman. That night, believing the assassin is in the judge's room, someone leaves a suitcase containing a rifle and a picture of mobsters Don Ferris and Sid Storm. Before Hardcastle can show the police, he is ambushed and the suitcase is taken. Hardcastle, unable to provide the police with any evidence, decides to visit Ferris. Although the mobsters are initially unwilling to believe the judge, they change their mind after Sid is murdered. Establishing an uneasy alliance, Ferry and Hardcastle put together the clues and realize that the hitman is a man named Lee Orlando. Reviewing Orlando's' recent history, Hardcastle discovers that the hitman has a connection with "Bucky" O'Neil, his main rival for the judge's award. Analyzing Bucky's court records, Hardcastle uncovers evidence that his rival has been fixing trials for the mob. Meanwhile, Ferris learns that Hardcastle is the assassin's next target. Due in part to the unorthodox teaming of Mark and the mob, Orlando is stopped and Hardcastle captures Bucky. Afterwards, Hardcastle, who does not win the judge's award, finds himself the unlikely recipient of an award from Ferris and the mob.

When the courts discover that a convicted felon named Randy Hopke had been defended by an incompetent lawyer, the original ruling is overturned and all charges are dropped. Hopke's release quickly prompts an argument between the judge and Mark. Hardcastle, having presided over the case, insists that, as originally determined, Hopke is guilty of assaulting his girlfriend Val Mickaelian. On the other hand, Mark, having known Hopke from when he was in prison, insists that the judge made a mistake. The two men, each hoping to prove they are right, set out to prove their respective positions. In the process of their investigations, both Hardcastle and McCormick realize that they are both wrong: While they learn that Hopke did not actually assault Val, they also discover that the released prisoner had planned the assault and was willing to serve a limited prison sentence to cover-up the fact that he had committed a murder during a diamond store heist. Theorizing that Val is probably working with Hopke, Hardcastle and McCormick follow her. As expected, she leads them to Hopke as well as the stolen merchandise. After an unusual "bus" chase, Hopke is captured and the case is finally resolved.

Not wanting to continue cleaning up the estate, Mark hires Millie Denton, his former prison cellmate's widow, as a maid. Meanwhile, Hardcastle begins looking into the suspicious death of a lawyer named Charlie Clarkson. Taking over Charlie's practice, Hardcastle interviews Loni Summers, a model that had previously hired Charlie to handle her divorce. Discovering the divorce is now off, Hardcastle checks into the background of actor Dex Falcon, Loni's husband. Investigating, the judge discovers that Falcon had secretly been receiving millions of dollars from an attorney named Wendell Price. In the meantime, Millie, who claims to be a psychic, has a vision of Mark's murder. Ignoring Millie's warning, Mark proceeds with the case. To Mark's regret, he is captured by Price, shot and left for dead. Thanks to Millie, Hardcastle locates Mark in time to save his life. Next, based on the evidence Mark had gathered, Hardcastle and the police, having already taken Falcon into custody, movie in and arrest Price. As the episode ends, Millie, shaken up by her visions, decides to quit and move in with her sister.

As the episode begins, wealthy businessman J.J. Norcross asks Hardcastle to run for mayor. Meanwhile, after city councilman Herb Austin goes head-to-head with Mann over a parks bill, a bomb explodes in the councilman's office and Austin is killed. Despite his campaign staffs assistance that he concentrate only on the election, the judge decides to look into Mann's murder. Deciding to help the judge, Mark sneaks into Mann's office and locates a map of possible park development sites. Checking out one of the marked locations, Hardcastle and McCormick discover an illegal toxic waste dump. Pursuing their investigation, Hardcastle and McCormick uncover proof that Mann had been bribed to change the site of the new park so as to cover up the illegal dumping. When Birdy Fletcher, the site's guard, asks to see him, Hardcastle realizes that he is probably being set up. As expected, Norcross, the mastermind behind the illegal operation tries to kill the judge. To Norcross' horror, a prepared Hardcastle and McCormick, turn the tables and close down the operation. In the process, Hardcastle discovers that Norcross only back his mayoral campaign so as to split the votes and give Mann the advantage. Later, although Hardcastle loses the election, he takes some comfort in the fact that Gilmore will most likely do a good job.

Questioning his maturity, Mark decides to trade in the Coyote for a more conservative car. To his surprise, his credit application is rejected due to an $18,000 default. Investigating, Mark discovers that his name was used in a real estate deal put together by Melinda Marshall, the girlfriend that had helped put him in prison. (As revealed in a flashback sequence, Mark, having foolishly placed his car in Melinda's name for insurance purposes, was arrested for stealing his own car.) Hoping to clear his credit record, Mark pays a visit on Melinda. Confronted by Mark, Melinda reveals that she had faked the real estate contract in order to win a car. When someone tries to steal the car Melinda won, Hardcastle realizes that there is something more going on than a simple real estate deal. Hearing that Melinda works for Ted Rubin, a man in his files, Hardcastle realizes that the real estate company is running a land fraud scram. Realizing that there is probably something hidden in Melinda's car, Hardcastle and McCormick conduct a search. As a result, they discover valuable stamps in the car and learn how Rubin has been transferring his money. Although Rubin arrives at the estate ready for a fight, he is captured thanks to the timely intervention of the FBI agents that had been investigating him. [During this episode, both Mark and Hardcastle have extremely subjective recollections of Mark's original trial.

After 10 years, the judge is paid a visit by his brother Jerry. Suspicious, Hardcastle begins to wonder when his brother, a habitual gambler, will ask him for money. Although he decides not to tell his brother, Jerry is in fact in debt to a hood named Manny. Hoping to find a way to get out of debt, Jerry decides to bet on the outcome of a high profile murder trial. Thanks to Judge Sheila Mooney, one of his brother's friends, Jerry gets all the particulars about the case in which model Tori Van Zandt is on trial for killing Harland Eagle, her fiancee. After a private investigator named Horace Munson provides Tori with a convenient alibi, Jerry is confronted by Manny about his debt. Drawn into the Van Zandt case by his brother's involvement, Hardcastle begins to look into the case. Searching Munson's office, Hardcastle discovers that the private investigator, who has since been murdered, lied in court. Hoping to incriminate Tori, Hardcastle publicizes the fact that he has evidence in the case. As expected, Tori tries to kill the judge and the police gather the proof they need to convict her. At the same time, the police also arrest Mooney.

Cleaning out his shed, Hardcastle comes across an old trophy belonging to Teddy Hendrix, his college roommate. Deciding to visit Teddy, who is now a basketball coach, Hardcastle walks into an attempted kidnapping. Since Teddy flees the scene before he has a chance to confront him, the judge visits his old friend's wife. Thanks to Fran Hendrix, Hardcastle discovers that Teddy has been having a disagreement with a man named Roy Barlow. Realizing that his best chance of solving his problems lays with the judge, Teddy decides to tell Hardcastle about how he has been fixing basketball games. Agreeing to help his friend come clean, Hardcastle arranges a meeting between Teddy and the district attorney's office. Before Teddy can testify, Fran, who has secretly joined forces with Barlow, lures her husband into a trap. Meanwhile, Fran also helps Barlow capture Hardcastle. Thanks to Mark and their old basketball team buddies, Hardcastle and Teddy are rescued. Additionally, Mark and the former team members capture Fran and Barlow.

After winning a Los Angeles area bar in a poker game, Sonny Daye, Mark's barely seen father, decides to run it with his son. With some financial help from the judge, Mark and his father prepare to reopen the bar as "McCormick's Bar and Grill". Meanwhile, Teddy Peters, the man who lost the bar to Sonny, is ordered to recover the bar by Doyle Madison, a reputed mobster. Despite an excessive cash offer from Teddy, Sonny, having given the bar to Mark, refuses to sell back the bar. Not willing to accept no for an answer, Teddy has his men rough up Sonny. After Teddy is killed in a drive-by shooting, Hardcastle realizes that there is more to the bar than meets the eye. Searching the bar, they discover that the mob has been burying bodies on the premises. Hoping to tie the bar back to Doyle, Hardcastle has Sonny arrange a meeting with the mobster. Taking the bait, Doyle makes a move to regain the bar. With the help of a bar full of police officers, Hardcastle and McCormick arrest Doyle and his men. Afterwards, the police impound the bar as evidence and Sonny, Hardcastle and McCormick are forced out of the restaurant business.

When Mark gets a date with a woman named Debbie Pledger, Hardcastle has to find a new player for poker night. To the judge's regret, Judge Mattie Groves, Lieutenant Frank Harper, and bailiff Charlie Masaryk, the other poker players, arrange to have Assistant District Attorney Freddie "Bummer" Bumgarner, a man Hardcastle despises, join them for the game. Meanwhile, a nearby liquor store is robbed. Needing a place to hide, robbers Tommy Kitchens, Crazy Horse and Joey Britton flee to Hardcastle's estate. Entering the judge's house, the robbers quickly take the poker players hostage. The situation worsens when they discover Frank is a cop and shoot him. Arriving at the main house to get some wine, Mark learns about the hostage situation. With some help from Frank, who was left in one of the bedrooms, Mark prepares a trap for the robbers. Thanks to an uncharacteristic heroic act on Freddie's part, Mark is able to successfully implement his plan and capture Tommy and his men.

In a change of pace episode, Mark begins to believe that Leprechauns are burying gold on the estate. Ignoring Mark's outrageous claims, Hardcastle concentrates on preparing the estate for an upcoming magazine contest. After Benny, Mark's mechanic, is assaulted by a group of men for information about a group of little people, Hardcastle admits that there may be some truth to Mark's Leprechaun story. That night, Mark and Hardcastle set a trap for the "Leprechauns". The trap works and Hardcastle captures the men who have been hanging around his estate. As the judge discovers, however, the little people are not Leprechauns but rather circus performers. Confronting the performers about why they are hiding out, Cluracan, the groups leader, explains that they are fleeing from communist agents that want to return them to their home country as well as Marvin, a circus promoter that had promised their services to Circus Maximus. As for the mysterious gold, Cluracan reveals that it is his family's money. The next day, communist agent Ivan and his men come to the estate disguised as employees of Ladies Garden Monthly, the magazine sponsoring the contest Hardcastle has entered. At the same time, Marvin and his men sneak onto the estate. With the circus performer's help, Hardcastle and McCormick manage to stop the agents as well as Marvin and his men. Later, Mark's continued suspicion that Cluracan's group are secretly Leprechauns seems to be confirmed when a rainbow leads to a mysteriously repaired Coyote.

While driving through Arizona on his way home from Las Vegas, Mark is surprised to hear the voice of Nick Damion, a rock deejay he idolized in his youth, on local radio station KKSB. Back in California, Hardcastle is working on a dedication for the Pioneers of Music Hall of Fame Museum. Hearing that the Museum needs a master of ceremonies, Mark suggests Nick Damion. Returning to Arizona, Hardcastle and McCormick try to learn something from Jeannine Alexander, KKSB's manager. After helping Damion, who has been using the alias of Joe Cross, out of a fake drug charge, Mark convinces the deejay to return with him to California. Trying to find out why someone tried to frame Damion (as well as why the deejay originally went into hiding), Hardcastle begins to investigate Kello Records, a company that had received a great deal of air time in the deejay's old radio show. At the same time, Damion, who had gone into hiding after discovering that music executive Joe Kello had killed a singer named Danny Phillips to cover up a payola scheme, realizes that he needs to go public with the story. Hardcastle's investigation proves partially unnecessary for the case is resolved when Damion publicly accuses Kello at the Museum dedication. Afterwards, Damion is shocked to discover that Hardcastle has uncovered proof that Jeannine is working with Kello. As the series' penultimate episode ends, Damion gets a new deejay job at a Los Angeles station.

As the final episode begins, Mark, who has secretly begun attending law school, is offered a paralegal job by Kenneth Malcolm, one of his professors. Meanwhile, Hardcastle, realizing that Mark's parole is up, decides to buy a car repair business, as a surprise gift for his friend. Upon hearing about Mark's job offer, Hardcastle, not wanting to stand in his friend's way, lies and tells his friend that he bought the company for himself. For his first assignment at law firm Malcolm, Hughes and Dewitt, Mark is asked to reclaim the possessions of Elsey, a resident of the Sunset Acres Retirement Home. Arriving at the home, Mark makes the acquaintance of Mimi LeGrand, a retired actress. Immediately liking Mimi, Mark is more than willing to comply when the former actress asks him to open a bank account for her. To Mark's surprise, he discovers that someone has already opened an account in Mimi's name. Concerned, Mark decides to go to Hardcastle for help. Before the two men are able to really learn anything in the case, they end up in jail as a result of a mistake made by Leroy, Hardcastle's assistant at the car company. While awaiting their release, Hardcastle decides to tell his friend the truth about why he bought the company. In response, Mark reveals that he has been going to law school in an attempt to follow in his friend's footsteps. Once released, Hardcastle and McCormick discover evidence that Malcolm and resident home manager Leonard Porter have been killing the residents and stealing their money. (They were able to move the money by secretly creating bank accounts in the seniors' names.) Armed with sufficient evidence, the crime fighting duo stop Malcolm and Porter. Despite the fall of his professor, Mark vows to continue attending law school. After selling the car business, Hardcastle makes a generous bet with Mark: If the ex-race car driver can beat him in a game of basketball, the judge will pay the law school bill. Due in the most part to Hardcastle's generosity, Mark wins the game.