A sniper terrorizes San Francisco on Halloween as a city-wide Blue Flu forces our SIU detectives to assume beat cop responsibilities. Joe tracks down a hard to find Halloween costume for Lucia.

Rick Bettina returns as the head of the S.I.U. Joe is accused of stealing 3 million dollars from a suspect. Harvey has a torrid affair with a woman he once arrested.

Nash gets involved with Irish terrorists, as well as his ex-wife Kelly (Serena Scott Thomas). Meanwhile, Joe looks after a party-minded Arabian prince awaiting a heart transplant.

An innocent man is scheduled for an execution. Nash, working the entire case from the 'Cuda, must bring the true killer to justice before the midnight deadline. Lucia's bullying of a schoolmate forces Joe and Inger to attend conflict resolution therapy, which only leads to more conflict.

An ex-60's radical uses runaway kids to commit a rash of crimes. Joe goes undercover as a shoe salesman to clear Maria of shoplifting charges. Caitlin accompanies Nash to a ritzy ball.

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.

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 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.

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.