Nash and company foil a jewelry heist ring posing as firemen. Nash hits a pedestrian and gets sued. But Caitlin has misplaced Nash's auto insurance bill, and he blames Caitlin.

Evan puts himself under suspicion after he takes $40,000 of drug money during a bust; Nash and the SIU take down a drug dealer. Nash and Joe guard a chimpanzee, while Jake Cage goes undercover as an animal extremist.

Nash and Joe arrive in Las Vegas, and locate assassin Roy McNeer's hotel room. His food is still warm, as Nash and Joe spot McNeer in a casino. Nash and Joe give chase, but are held up by the hotel security guards, as McNeer escapes. Nash and Joe check into the hotel - Pepe is the concierge. They locate McNeer's girl, Vivienne Reed, and she agrees to tell Joe if McNeer calls her. The truck full of half a billion in laundered cash is hijacked. The two thugs contact Tony B to ransom the truck for $50,000. Tony B and the SIU meet them and get the truck back. Harvey, Evan, Officer Ronnie and Tony B go to Las Vegas with the truck full of money. Jake Cage shows up in Las Vegas too, with orders from Caitlin and the Mayor's Office to bring back Nash. But Jake agrees to help Nash instead after an altercation. Nash meets with Ellen Holiday. She fills Nash in on the rest of the DEA investigation. Jimmy Z works for a drug king pin coming in from Shanghai - they have ordered the hit on Police Chief

Hot on the trail of a murderous criminal from Chicago, Nash teams up with a KAREN DECKER, a cop from the Windy City who's in every way his equal: smart, competent-and yes, sexy. Sparks fly between them as they track down the visiting villain together -until, that is, Nash learns his newfound partner is not as perfect as she's led him to believe. Joe, meanwhile, hires a pet psychologist to cure what ails Nick's racehorse, Mr. Woody.

A juror becomes a vigilante avenging murder victims. Caitlin and Joe go in on a donut business venture. Evan is arrested and calls Cassidy; Cassidy finds a new boyfriend.

Wearing his brother's uniform as a motorcycle cop and impersonating a police officer, a deranged man imagines and talks to his dead brother. Nash adjusts to his break-up with Caitlin; Nick fails his driving test; Cassidy asks Evan for help to move back into a Berkeley apartment.

Nash goes undercover to stop a high-end heist artist. Joe helps a restaurant critic who receives death threats; Evan is back in the SIU; Caitlin takes an administrative job within the department; and Harvey helps out a troubled 12 year old boy.

Nash has to deal with the fact that Joe may have 72 hours to live after being exposed to a deadly virus while Nash & Joe investigate a drug theft from a research lab.

Nash and Joe get a tip from Tony B that there is a hit out on Chief of Police Frank Girard. But it's already too late, as the Chief's car is shot up - the Chief and his driver are killed. Nash and Joe arrive to find the carnage. The Chief was a close friend of Nash's. There was one driver, one triggerman, using a bright red Impala. The Impala crashed into a taxi, leaving behind a paint sample. Thanks to Caitlin's suggestion, the SIU and the Embarcadero station are sharing office space in the barge. There is total chaos, as Joe is forced to share a desk with Jake Cage. Tony B is interrogated. Tony B has a new business - Bay Area Switches. The trucking business is really a front to ship money to Las Vegas to be laundered. Tony B's contact is Ellen Holiday. Holiday is in contact with the assassin of the Chief and with Jimmy Z, head of the money-laundering operation. Holiday is arrested and questioned, but she reveals nothing. The red Impala is found, tracked to a Melvin from a wrecking ya

Nash and Joe have a task of escorting a secret key witness from the Witness Protection Program to San Francisco to testify in an important SIU-related case. They fall under gunfire. Nash realizes there's a leak somewhere on the prosecution's team. He enlists the help of Stacy to protect them until he can solve who it is and get the witness safely to San Francisco. Cassidy is stood up for a date and decides to go out with J.J. instead.

A psychologist establishes an insanity defense for her patient while they plan bank robberies. Nick wants to become financially independent by marrying a rich widow. Evan shows up for work drunk, forcing Harvey to confront Evan's substance abuse problem.

A married woman is murdered by her lover and his wife. Evan is beaten up trying to free his girlfriend/hooker from the clutches of a pimp. Joe takes Evan in, but Evan attempts suicide. Boz Bishop asks for a promotion at the detective agency.

A gang of female prisoners escape in search of five million dollars in bearer bonds, while Nash helps the woman framed for the theft of the bonds. Joe has trouble with a delivery boy, while Cassidy considers a career with the CIA.

Nash is stuck with an eleven year old delinquent who's the link to busting a drug kingpin. Joe is reunited with his grown son J.J. and Nick wreaks havoc with Nash's attempt to find him a live-in nurse.

Nash and Joe cut a deal with Carlos Casas, a gangland money launderer, offering him a new identity in exchange for his testimony.

Joe goes undercover inside State Prison to bring down a ruthless Mexican gang leader who put out a hit (from behind bars) on a SFPD undercover cop who had infiltrated the Mexican Mafia. Nash runs the investigation on the outside, hoping to fulfill a promise to the dead man's widow by catching the trigger man. Naturally he'll have to overcome the distraction caused by Nick, putting together his will, who discovers some long-forgotten wealth.

Nash and Joe butt heads with the leader of a team of Urban Commandos who has been hired to protect an inner-city community. While awaiting the birth of the new baby, Joe searches for the family crib that he lent to Nash seventeen years ago.

When a reporter is murdered while covering the new ""French Connection"", Nash comes face-to-face with a startling revelation - his brother, a Vietnam MIA, thought dead for the last 24 years, may be alive and in San Francisco. Meanwhile, Lisa's sister, Lynette, arrives to house-sit at Lisa's indefinitely.

When a controversial Latina actress is shot and killed, suspicion turns first to her former lover, then to a crazed stalker. Evan comes back to work after surgery, but Cassidy wants nothing to do with him. Caitlin moves in with Nash, and causes strife between her and Nick.

An embezzler with a twin, along with bumbling Rick Bettina, confound the efforts of Nash and the SIU to recover stolen city funds. Caitlin tosses Nash's baseball out the window after they miss their flight to Jamaica.

A gang war erupts - Nash and the SIU puts a drug gangster and his crew out of business. Cassidy comes on to Evan as their lovemaking is shown on a live camera web site. Joe and Nick get involved in a tax scam with Nick's racehorse - Mr. Woody, as the horse is once again fit to race.

Nash and company foil a failing restaurateur's kidnap plan to ransom his nanny's child. Nick has sex with Bridget, Caitlin's inept maid. Inger returns for a visit, but leaves for Sweden again. Cassidy has a friend attempt suicide because he can't get a date with her.

Cassidy finds an apartment, only to be mistaken for the previous renter who has stolen money from drug dealers. Lonely Joe carries on an online romance, but the other ""woman"" turns out to be Pepe. Evan bottoms out in his broken relationship with Cassidy

Nash and the SIU discover the Cell Phone Killer's intentions are to kill his doctor. Lonely Joe keeps having erotic dreams about Caitlin. Evan gets fired from his bartender job.

Frankie Dwyer returns again, putting out a contract on Nash's life while smuggling heroin inside of tofu containers. Nash and Caitlin's relationship is strained; Inger sets up Nick with her mother Ulla; Evan is born again in a baptism.