A serial killer who picks up passengers in a cab and then murders them stalks the city; Rachel realizes that Nash is being set up by a superior who wants to accuse him of stealing department money; Cassidy struggles with whether she wants to continue to be a cop.

A robbery at the Fillmore during a concert by Phil Lesh prompts Nash to investigate a soccer coach and his daughter, a stolen motorcycle and a record producer.

Cassidy is suspended following her involvement in the fatal shooting of a bystander during a bank robbery and becomes the target of department cronies who want to use her to get rid of Nash.

Harvey becomes attracted to a fellow "Deadhead," a mysterious woman who is the target of a murderous stalker; Joe is promoted to lieutenant, but discovers that his new duties mostly involve paperwork; Nick injures his leg and makes life difficult for Nash and Cassidy, who are trying to take care of him.

Nash begins to believe that a 17-year-old boy involved in the Southeast Asian drug trade may be his missing brother's son; Cassidy starts dating a plastic surgeon and considers getting breast implants.

Nash tries to track down the builder of a heavily armed robot that robbed a convenience store and killed a cashier; Nick tells everyone that he is going to die on his next birthday; Joe learns that a valuable item was behind a painting he sold at a garage sale.

Nash hunts for a vigilante who claims he's helping solve crimes by murdering deadly criminals, including a serial rapist; Nash's distant and eccentric cousin, who is also a cop, visits from Scotland.

Nash and a Federal marshal are taken hostage by a Miami drug lord who wants to exchange them for a witness who's scheduled to testify against him in court; Joe tries to get out of being audited by the IRS.

Nash's former lover Tamara Van Zant forges his name on a marriage license and claims to be married to him in order to protect herself from a thug out to kill her; Nick pretends to be romantically involved with a lesbian friend to deflect suspicion from the woman's son, a high-profile gangster from Philadelphia.

Rachel is accused of murdering a man who was helping the police investigate corruption in an accounting firm, but Nash is convinced she was framed; Joe tries to find a ringer to represent the department in an arm-wrestling contest.

Nash is suspicious of a teen's involvement in a brutal ambush that targeted a pair of lawyers, leaving one riddled with bullets and the survivor barely wounded. Meanwhile, Joe is burdened by an unwanted roommate, and Cassidy begins seeing Rachel's blind date.

Nash and Joe help a Canadian Mountie track down a ring of poachers who are illegally selling bear gallbladders, which are supposedly valuable as medicine and as an aphrodisiac; Rachel fears she may be pregnant.

Nash becomes involved in a case involving a local con man, Tony B, who fakes his own death to escape from a mob boss he ripped off; Joe discovers that his mother-in-law is smoking marijuana for medical purposes; Nick tries to save a historic building in which he once placed a time capsule.

A madman guns down five people in an elevator, but leaves a young news reporter alive. Unfortunately, she's as interested in reporting the story as she is in catching the killer. Also: a woman steals Joe's car and commits a robbery using it.

While tracking an old nemesis who has escaped from prison, Nash and Joe become trapped in the basement of an abandoned building---which is set to be imploded.

Nash tries to stop a deadly game in which participants shoot and kill each other until only one is left alive; a wealthy family's gardener is murdered and Nash starts to fall for a beautiful new investigator working the case.

Nash and Joe discover that someone is using their detective agency's name to stir up business for themselves, and that one of the impostor's clients is out to kill Nash; a college student is believed to have drank himself to death, but Cassidy suspects he was actually murdered; Hank intervenes when his neighbors get too rowdy.

When Nash and Joe investigate a carjacking, they uncover an international ring of drug smugglers headed by ex-soldiers.

Nash pursues a group of modern-day pirates who target and rob wealthy partygoers; a nun, who claims she's a virgin, says her pregnancy is a miracle; Joe goes to extreme measures to catch a speeder on his street.

Nash pursues an old flame who is involved with an arms dealer; Joe takes a private domestic case to discover if a symphony conductor is having an affair; Cassidy struggles to let go of Evan's memory when she is asked out on a date.

Cassidy's life is in danger after she comes face to face with a hired assassin who gunned down two men involved in creating and marketing synthetic diamonds; Joe takes a private case involving a stolen wine collection that is being held for ransom.

Nash faces a difficult choice posed by a revengeful madman: kill Joe or a bomb will explode somewhere in the city. "You can kill one or you can kill hundreds," the would-be bomber says. Elsewhere, Cassidy, now an officer, starts working for her dad; Nash hires a new investigator with a checkered past; and Joe buys a house after he's forced to move.