A deranged ex-cop has planted a bomb in the city and will only give the location to Nash is Nash kills Joe. Meanwhile Nash must also handle bringing Harvey a new partner, evicting Joe and Inger, and Cassidy's first day on duty. Inger and Joe purchase a house that seems to good to be true.
Nash investigates a series of robberies committed by an organized group targeting wealthy people. Joe seeks help in stopping a neighborhood speeder. Meanwhile Joe takes a side gig to find a missing cat on top of a gig Nash takes on to solve the mystery of a pregnant nun claiming immaculate conception.
Nash accidentally stumbles upon a group of Marine's who've stolen D.E.A. property, lead by an ex sergeant of Babcock's. Harvey finds out Babcock has yet more secrets that have been kept. Nick sets up Nash on a blind date with his lady's daughter, whom has more going on than meets the eye. Joe has troubles with his contractor.
Nash and Joe find not only themselves but their private investigators business impersonated. Harvey finds himself as the deciding vote in the neighborhood over a contentious issue. Cassidy investigates the supposed accidental death of a young college man.
Nash and Joe investigate a group of men killing each other to score points in a real life video game battle. Boz seeks Nash's help to clear himself of a murder charge, which also leads to surprising discoveries about Boz.
Rick Bettina escapes from prison with the help of an old foe of Nash's, leading on a hunt for him and the missing money. Joe has to deal with his contractor and his architect having a big fight and splitting.
A news reporter with a murderous stalker impedes Nash's investigation to help her. Joe decides to sell Inger's old car himself but things go bad when it's stolen and Joe is accused of having an affair. Harvey asks out a woman he accidentally gets naked pictures of.
Tony B is supposed to be dead, but his funeral leads Nash back to an old nemesis and blast from his past. Nick gets arrested for protesting the impending demolition of a building. Cassie goes on the hunt to find why this building is so important to Nick and how it ties into his past. Joe is accused by Inger of using marijuana, and Ulla is to blame. We find out about Nash's grandmother.
An old acquittance of Nash and Joe's, a Canadian cop, is on the run from Canada and on the hunt in the U.S. for a couple of bad guys. Nash has McCabe write Cassidy's 20-week probation report. Nick has troubles with another pier fisherman that gets blown way out of proportion.
Nash and the S.I.U work to clear one of their own when McCabe is framed for a murder she didn't commit. Meanwhile, Dominguez looks for some muscle within the department to compete in S.F.P.D's annual arm wrestling competition.
Nash's estranged wife Tamara Van Zant shows up with millions of dollars in her bank account and a murderous former son-in-law out to get the family fortune back. She also gets mixed-up with someone that may put an end to her ways.
Nash is reunited with an old familiar friend who is involved with gangsters out of Miami. They kidnap Nash in order to get a federal witness released from protective custody. Dominguez gets audited by the IRS.
Nash and the S.I.U investigate the shooting of two high profile lawyers by a former client, one of whom is killed. Despite the evidence, Nash suspects it's a set up. Dominguez buys a house without reading the purchase agreement.
Nash and the S.I.U look into the world of battle bots and their builders to find out who's using their bots to rob convenience stores and armored cars. Dominguez thinks he's found an original copy of The Declaration of Independence.
Nick tells Nash he thinks his son, Bobby is back and following him. They think he's missing in action in Vietnam but Nash knows he's alive and is in the drug business in Southeast Asia. Nash sees someone following Nick but it's not his brother, he's too young but he does look like his brother in his youth. Someone pulls a gun on him so Nash intervenes. He learns the one with the gun works for a drug dealer who also operates in Southeast Asia. Nash finds the young man and talks to him learns that he is the son of Nash's brother. And that his father and the other drug ...
A psychotic man out to avenge his brothers death is tracking down all the Joy Larson's in San Francisco, killing some of them, until he finds the one that was his late brothers girlfriend. Dominguez is promoted to Lieutenant.
Cassidy and McCabe walk in on a bank robbery and shoot it out with the perpetrators. One of the customers is killed, but it's unclear who's gun the fatal shot came from and Cassidy is suspended pending an inquiry.
Harvey is enjoying a night out at a benefit concert when two beautiful young women use a front end loader to bust through the wall and then make off with all the proceeds on a custom Harley motorcycle. The S,I,U tracks them down.
Nash and company track down a serial killer who picks people up in a cab; Rachel reveals the truth about what she's been up to at the SIU; and Cassidy debates whether she wants to be a cop anymore. Though not officially advertised at the time of airing, this was the series finale.