The detectives of the 15th Precinct investigate a double homicide involving one of their own, an alcoholic cop who seems to have done the right thing, but can't remember key details about the incident.
John Irvin fears the worst when Dolores disappears. The detectives search for a body when a mentally ill man confesses to raping and murdering his girlfriend's daughter. Two brothers run their own investigation when their sibling is murdered.
Sorenson and Sipowicz investigate the murder of a nine-year-old girl whose body was discovered inside a locked basement. Medavoy and Martinez assist an elderly man who believes that his young girlfriend was pressured into embezzling money from him.
Sorenson and Sipowicz investigate when a fellow officer shoots a drug dealer; Russell and Kirkendall intercede on Gotelli's behalf when a disgruntled man repeatedly vandalizes his mobster neighbor's car.
Mike Roberts is found dead. John reveals a connection between Roberts and Cullinan, who was with Dolores when she died. Mike left behind a memoir detailing some of his work. Jill goes undercover as a drug-addicted hooker.
Dornan causes problems at an AA meeting and Andy asks the Lieutenant to talk to him. Dolores' father accuses the squad of withholding information from him about his daughter's murder. Jill splits from Cohen.
ADA Costas prepares for the trial against Cullinan, and chooses Sorenson to testify over her husband. A man is shot dead in his apartment, and his wife's story about Latinos looking for drugs doesn't add up.