Bumper goes back to the Police Academy to take a course designed to update veterans in modern techniques. An ex-con has a job, but an informer says he is in on plans for a big robbery.

Bumper tells down-and-out bum Joey to stop disturbing the police when he keeps confessing that he's the one responsible for raping and murdering four women. But when Joey begins to give details which only the cops and the murderer know, Bumper realises that Joey has become the sounding-board for a maniac.