shooting of a foreign exchange student by Tim's cousin, Jim (portrayed by David Morse). Pembleton was convinced that Jim, if only in the few seconds before the shot was fired, was motivated by racism. Pembleton investigates the case vigorously, and is outraged when Jim is acquitted. In the Season 5 episode "Betrayal," a case involving a man beating his stepdaughter to death causes an emotional Bayliss to tell Frank about how his uncle sexually abused him as a child, and his father was dismissive when told about it. When Frank attempts to be consoling, Bayliss rebuffs him and ends their partnership, causing them to become cold and indifferent toward one another. They make amends after Mary's leaving causes Frank to tentatively reach out. In the Season 6 finale, during a gun battle with members of dead drug kingpin Luther Mahoney's organization. Frank takes aim at a suspect but cannot bring himself to fire. Bayliss pushes Frank out of the way. As a result, he is shot and critically wounded. Since Mahoney was shot by Detective Mike Kellerman, of Lt. Giardello's squad, Giardello became suspicious about the circumstances of Mahoney's shooting, even though it was officially ruled justified. When he orders Pembleton to re-investigate the shooting, Pembleton interrogates a hostile Kellerman, who finally admits, without remorse, he shot Mahoney when the dealer's weapon was pointed downward, endangering no one. Pembleton met Bayliss's mother, Virginia, while Tim recovered from surgery. She told Frank what Tim thought of their friendship: "He thinks the world of you. He says you're his friend. He says you're not a person who has friends, but he's your friend." Shortly afterwards, Pembleton and Mary say a prayer for Tim, during which Pembleton is visibly distraught (something he is almost never shown to be in the course of the show) and refers to Tim as his friend. Disgusted by Giardello allowing Kellerman to resign without charges and tormented by guilt over Bayliss's shooting, Frank quits the force and is absent for Season 7. Retirement and Return Pembleton retires from the force after Bayliss is shot, but two years later, Bayliss and Pembleton (who is now working as a professor at a Jesuit college) both come out of retirement to help solve the shooting of their former lieutenant, Al Giardello. After the case is solved, Pembleton inadvertently "solves" one final case when Bayliss confesses to murdering serial killer Luke Ryland.