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.

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.

Mark, Jesse, and Amanda are trapped in a hotel when it's quarantined after a deadly virus is released. They struggle to contain the virus, while at the same time trying to locate its origin. Meanwhile, a scheming seductress carries out her plan, using the virus as a diversion to rob a nearby bank vault.

Two fiancées plot to murder the bride's father on their wedding day. The two review their perfect plan the night before the wedding. Unfortunately murder is never as easy as one might plan.

Dr. Sloan crusades to keep a physician-assisted-suicide advocate from practicing her trade.

Mark stumbles onto a kidnapping case when the kidnapper accidentally calls the Sloan residence with a ransom demand. Steve runs to phone booths across the city a la Dirty Harry to safely rescue the child.

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 investigates a series of seemingly unconnected murders committed by terminally ill patients, to find the hidden thread.

Jesse saves a woman, Chloe, in a traffic accident that claims a jealous lover forced her off the road. Jesse looks out for his patient when her ex-boyfriend threatens her. Jesse rushes to Chloe's aid when her life is threatened by her boyfriend, and inadvertently kills him. Jesse finds himself the victim of Chloe's 'fatal attraction' as she pursues him voraciously. It gradually becomes clear that Chloe was the aggressor in her previous relationship.

The Community General doctors are dragged back into the world of network television when producer Jackson Burley revamps the pilot for Dr. Danger, the television program based on Dr. Sloan. Mark and Steve investigate when Danger's competition, a masked magician who reveals the profession's secrets, is murdered, possibly as a ratings ploy.

The hospital is the scene of a manhunt when a corpse comes to life and attacks Amanda, then leads Steve and the police on a chase throughout the entire building during which he kidnaps Jesse's girlfriend Steve. Mark learns the fugitive is on the run from NSA agents, who claim he's an international terrorist.

A serial murderer strikes Community General every hour on the hour, choosing victims who've been seriously injured but 'brought back to life'.

Amanda enlists Jesse's computer-nerd friends to find a killer, after she accidentally surfs across an on-line murder. Meanwhile, Jesse's girlfriend, Susan, comes down with a case of food poisoning after dining at Barbecue Bob's.

Jesse's car breaks down while he and Susan are on their way to a fun-filled vacation in Carmel. The two are stranded in a small town where Susan spies a supposedly long dead beau, Greg. They eventually discover that he faked his death in order to plunder a shipwrecked vessel undetected. The townsfolk, all in on the scheme, murder Greg and pin the blame on Jesse and Susan.

A criminal with a death wish stalks Steve.

Steve enlists troubled teenager (he sure looked older than a teenager) Tommy to work as community service at a boxing club after too many brushes with the law. Tommy tries to control his temper. Mark finds that the club's sports drink is drugged, promoting aggressive tendencies in many of the boxers.

Mark matches wits with a murderous network executive.

Carter and Caitlin kidnap Mark, forcing him to mastermind a 100 million-dollar theft. On the outside, Steve and Ron collaborate to find Mark. Meanwhile, Jesse and the Sloans buy a barbecue joint.

Mark, Steve, Jesse, and Amanda are all trapped in the rubble of Community General in the aftermath of the bombing. Mark tries to shake off the numbing effects of the explosion in time to save Amanda, who's suffering from a punctured lung and broken collarbone. After the dust settles, the hunt for Caitlin Sweeney begins. It's discovered that the Sweeneys belong to a terrorist organization, R.O.A.R.

Shadowy figures haunt Jesse after he returns after being missing five days and believes aliens may have abducted him. Mark and Steve try to figure out what happened to him, while Jesse tries to stave off hallucinations, clandestine midnight meetings, and secretive government agents.

When a best-selling mystery author comes down with writer's block, she commits a murder herself in the hopes of stimulating her creative juices. The delusional author has help from her fictional heroine, Danielle Slade.

Absurdly bland episode lacks the usual Goldberg/Rabkin sizzle. Two female vice-officers uncover four corrupt female homicide cops who murder felons to harvest their organs for those more deserving.