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.
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.
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 ...
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.