Mickey adjusts to her new duties as liaison. Billie returns from rehab and wants back into Nicco's life. Ali's attempt to tie a gang wannabe to a double murder goes in a surprising direction.
A woman who Len previously suspected of murdering her wealthy husband returns to town . . . to get married to another wealthy man. Len is determined to stop her before she kills again.
Christine's brother Aaron dies after being hit by a car, and she presses for a murder investigation. When that doesn't happen, she infiltrates a group of car street racers without authorization. Len and Ali investigate the death of an infant.
When Christine identifies a teen-aged John Doe from a partial skeleton, the boy's mother is someone Pawlachuk knows. His father turns out to be someone everyone in the squad knows.
Len and Nicco work with a homicide detective to look into the connection between a cold murder case and the more recent murder of a gay-bashing thug at the same night club. Mickey uses a new computer program to find an arsonist.
A former homicide detective, who was demoted to beat cop 15 years ago for publicly hanging a suspect off a bridge, is promoted to the Cold Squad. He and Nicco work on the case of a body found encased in concrete of a building under construction.
Len meets the "victim" of one of his old Homicide cases . . . alive . . . in the holding cell. Mickey is confronted with new developments in a cold case involving a 4-year-old girl, whose decapitated body Mickey found when she was a patrol officer.
Ali and Len question several members of a swingers club about the death of a financial planner who was also a member. Nicco is cleared to rejoin the squad.
Ali attempts to build a murder case against John Watts before he is extradited to Texas for the murder of a Texas Ranger and a possible death sentence.
Ali is affected by meeting the daughter of a jailed murderer, who commits suicide after pleading his innocence to Ali. Sonia, who is working undercover in a strip club, puts pressure on Len to leave Wanda.
Nicco reports for his first day as Acting Sgt. on the beat. Len pumps his snitches for the whereabouts of Valentine by using an offer of $500 for a lead. Ali runs into official interference in the Rhaman suicide investigation.
