Nash and Williams stop a car-jacking and the suspect is then linked to a murder case that Callaghan has been assigned to. However, the murder charges will not stick as the bullet was never found at the scene. Callaghan enlists the help of McNally to watch a witness who actually has the bullet lodged in his skull after killing the victim. The witness manages to get away leaving McNally to find him before he is killed for what he knows. Despite being able to find the witness, he dies as a result of an operation to remove the bullet.