This adaptation of Auber's 1830 comic opera has Stanlio and Ollio serving the notorious thief Fra Diavolo.
Masquerading as the Marquis de San Marco, Fra Diavolo (Dennis King) in a coach is shown jewels by Lady Pamela Rocburg (Thelma Todd). Although Zerlina (Lucille Browne) loves Lorenzo (Arthur Pierson), her father says she must marry Francesco. Stanlio (Stan Laurel) and Ollio (Oliver Hardy) are robbed of their life savings on the road and decide to become bandits. A father of sixteen pleads with them; they cry and give him money. People run from the terrifying Diavolo; but Stanlio and Ollio hold him up, Ollio saying he is Diavolo. Diavolo says that Stanlio must hang Ollio to go free. Diavolo learns from his gang that robbed the jewels that they missed the diamond medallion and the money. Ollio's weight breaks the branch; so Diavolo makes Stanlio and Ollio his personal servants to the Marquis.
Lady Pamela keeps the money in her petticoat and the medallion on her chest. At an inn a reward is posted for Diavolo's capture. Stanlio and Ollio capture Lord Rocburg by mistake in the Marquis' room. They run from Diavolo and try to hide. The Marquis gets sleeping tablets and puts them in wine. He tells Stanlio and Ollio to take it to Rocburg; but Stanlio drinks it. Diavolo tells them of a signal. Stanlio keeps falling asleep. Ollio and Stanlio manage to climb up to the balcony. After Zerlina undresses while singing about her figure and goes to bed, Diavolo finds the medallion. Soldiers march in, and Lorenzo climbs the balcony to Zerlina.
The next day Zerlina is to wed Francesco. Pamela says she was robbed. The Marquis accuses Lorenzo and finds the medallion in his cape. The Marquis tells how he saw Diavolo once and sings his song, "Be Every Moment Be Gaily Passed." The innkeeper sends Ollio and Stanlio to the cellar for wine, and Stanlio gets drunk. The Marquis asks Pamela about the money and learns that she guards it near her. He wants to see her in her robe again, so he can get the money. Lorenzo places a guard around the inn and fights Diavolo with swords. Lorenzo then arrests Diavolo and gets the jewelry back. Diavolo gives Lorenzo the money so that he can marry Zerlina. Diavolo, Ollie and Stanlio are lined up to be shot; but when Stanlio waves his red handkerchief, a bull charges, and all escape.
The places Pamela hides her valuables provide sexual innuendo. Stanlio and Ollio present their usual comic antics, and the music vitalizes the story. The eagerness of the poor to rob the rich reflects the economic pressures of the time.