S4·E15 The Princess and the Pig

A disturbance call leads the officers to a nightclub where a singer named Kathy is strung out on drugs, and clings to Reed on the way to the hospital, telling him someone is trying to kill her and give her drugs. Narcotic detectives decide to assign Reed undercover as an AWOL soldier with a large stash of heroin to sell. Reed makes a deal, but Kathy blows his cover, and Malloy saves his partner from being killed and helps bring down the dealers.