Newly retired detective Harry Trumble returns to the force when it appears 'The Clown Killer', a murderer Trumble chased for more than a decade, has emerged from obscurity to kill again. Mark is reluctant to help Harry investigate the Clown, in part due to a rift between the two, but also because Mark suspects Harry has something to do with the Clown's reappearance.

Dr. Sloan and Amanda investigate when the co-pilot of the airplance carrying them to a medical conference is murdered and the remainder of the flight crew are incapacitated with a mysterious illness.

Steve heads up the investigation when a serial cop killer is on the prowl, while inadvertantly dating the killer.

Dr. Sloan investigates when an unpopular colleague drops dead while performing an operation. Mark investigates his fellow doctors when tests reveal the deceased was poisoned.

Hospital horticulturist Claude is revealed to be an escaped convict living under an assumed name for the past 10 years. Mark fights to shelter Claude from extradition while striving to prove his innocence.

A young woman is assassinated while Dr. Mark Sloan is examining her, setting off an investigation that plunges Mark into dark memories of his own childhood.

An unhappy politician's wife guns down her husband in an underground garage. Mark sees through her alibi and attempts to confirm his suspicions.

Two women involved in a love triangle plot to murder a man, take his millions, and leave the country. Dr. Sloan investigates after his friend's mysterious disappearence.

Dr. Sloan investigates a free health clinic after several homeless people turn up dead... with missing organs.

A burglar inadvertently becomes infected with a deadly virus. Dr. Sloan and Jesse are subsequently exposed to the virus after Jesse stumbles upon the thief's dead body. Both Mark and Jesse are confined to Mark's home while Steve and Amanda investigate the drug company that manufactured the virus, in the hopes of discovering an antidote before Jesse runs out of time.

Mark investigates a 30-year old murder when the body of his old mentor is discovered entombed in a wall in the hospital.

Mark aids an old friend, Joe Mannix, in solving a 25-year-old, unsolved murder.

A wealthy woman and her boyfriend dupe Mark and plot to murder her husband.

Dr. Sloan is stalked by a mad bomber whom he helped incarcerate. Norman and Mark are the main dissenters in negotiations to sell the hospital to a corporate raider.

Steve becomes embroiled in political intrigue after the murder of a city councilman's wife appears to be part of a larger political strategy. Steve investigates two mayoral candidates, the councilman and the chief of police, as well as a rogue detective and his partner, all with strong motives.

A spat between a girl and her boyfriend leads to an apparent murder, leaving the girl and her mother with a dead body, just as dinner guests Mark and Amanda arrive. Panic sets in, when the body disappears, the power goes out, the roads are impassable, and the attacks begin.

Steve and his abrasive, confrontational partner are confined to a therapy home for 90 days after Steve shoots and kills a fleeing suspect. Steve's partner, Reggie, believes his wife and daughter are being held hostage by his nemesis, a belief that is furthered by a series of delusional events. On the outside, Jesse and Amanda work with Tanis Archer to solve the murder of a lab technician.

Steve goes undercover as a doctor in a private community after several mysterious deaths occur within its confines. Steve is 'aided' by a tabloid reporter posing as his wife.

Steve nearly dies in a car accident and think a murder happens. No one believes him.

Mark must find out why his dad left him as a child.

Dr. Sloan tries to save Jesse and Amanda from a murderer who is out to kill them in order to obtain a multi-million dollar inheritance.

A tell-all book written by one of Amanda's vindictive old college roommates contains embarrassing secrets of all four roommates. Dr. Sloan tries to discover what happened when the author is found dead and Amanda is the main suspect.

Dr. Sloan goes undercover at a convent when mysterious circumstances surround a murder.

Dr. Sloan takes in an abandoned young girl found at the scene of a murder, while Steve and Jesse go about tracking down the killer.

One police officer is accidentally shot by another during a raid gone wrong. Dr. Sloan investigates the victim's wife, the shooter, and a conniving lawyer when he suspects foul play.