“Shorty” Matthews having recently been released from prison visits his girlfriend in London only to discover her murdered. Fearing he will be wrongly accused of being the culprit he disappears amongst the long-distance lorry driving community. Meanwhile, the real killer, unassuming ex-schoolteacher Walter Hoover, continues to prey on London women. As Shorty had feared he has become the main suspect. He returns to London with old flame Molly to prove his innocence.

A disgraced school master, Benjamin Twist, is mistaken for a tough prison governor and assigned the charge of a prison for particularly hardened criminals. Believing he is being sent to a school rather than a prison, he celebrates accordingly only to find that his drunkenness accidently lands him on the wrong side of the prison bars. The Governorship is eventually restored to him, and he sets about popularising himself amongst the convicts by turning a blind eye to their shady dealings.

Dr. Benjamin Twist (Hay) and his pupils become involved with art thieves on a trip to Paris. Hay’s seamy schoolmaster act is supported by a fine cast including Charles Hawtrey and Lilli Palmer.