Steven Leight was a New York businessman. He was having an extra-marital affair, and decided to kill his wife, Beverly, leaving him free to live, full-time, with his mistress. He took his wife to an isolated part of Central Park, and shot her in cold blood, then took her jewelry to make it look like a robbery.
After the shooting, Leight went to a nearby bar and steadied his nerves with a drink before calling the police. By accident, the newly-appointed Latvian ambassador happened to be in the bar at the same time, and mistakenly received Leight's coat from the bar's cloakroom, which still had Beverly's jewelry in the pocket. A few minutes later, Leight, receiving the ambassador's coat, realized the switch and panicked, following the ambassador back to his hotel, and shooting him and his two bodyguards in an elevator. Leight then switched the coats back and ran out, past Adrian Monk. Leight shielded his face with his coat, but Monk was still able to see and remember the shape of his left ear.
Leight pretended to be a grieving widower; but when he was interviewed on the TV news, Monk saw him and recognized his ear, and patient investigation linked him to the murders of his wife, the ambassador, and the two bodyguards. Leight was arrested for the charge of quadruple-homicide.