Tommy Burke, a good-natured young plumber who refers to his monkey wrench as his pipe organ, is unaware of his inferiority complex. One day he learns that an eccentric uncle has died, leaving him a brown derby said to bring good luck to its wearer. Meanwhile Edith Worthing and her Aunt Anna are expecting Edith's wealthy uncle, Adolph Plummer, from Australia. On a call to their house, Tommy is mistaken for the uncle, being announced as "a plumber," and soon a mutual romance develops with Edith. They are wedded by mistake when serving as witnesses to marriage by elopement. Farrell, a rival for Edith, learns of Tommy's deception and persuades Edith to elope with him; but Tommy follows in hot pursuit, in his pajamas and derby. At the last minute, a message arrives telling Edith that she and Tommy are already married.

A well-respected boxer is framed by his enemies in the death of a policeman during a raid on a local gambling establishment. He is convicted and sentenced to death and his friends seek to find the real murderer.