Bob Naughton and Eddie Connolly are identical-twin brothers that were separated in infancy. Bob is raised by a rich lawyer, has all the advantages, but is a drunk with no moral character. Eddie is a pianist in a speak-easy but a man of high character. Bob commits a murder and Eddie is blamed and faces life in prison.

Michael Lanyard, a reformed cracks-man, adopts Adrienne, the daughter of an old friend, and goes to Southampton to attend a party celebrating her engagement to Bobby Crenshaw, the son of a wealthy society couple. The Count and Countess Polinac, international jewel thieves, also attend the party, and Count Polinac forces Lanyard to open the safe containing the jewelry of the guests by threatening to expose Lanyard's criminal past. Lanyard forestalls the count, however, and protects the valuables. The count and countess are arrested, and Michael's secret is kept safe.

In this entry in the Lone Wolf series, the first to have a soundtrack, the jealousies of the King and the coquettish Queen are chronicled. When His Majesty learns that his wife has given the ring he gave to her to her lover, the King plans a large ball and demands the she wear the token. As her lover is a military attache, he is not in the palace, and the queen must send her lady-in-waiting to bring it back. En route, the lady meets a thief and they team up. She does not know that he has been dispatched by the King to steal ring from the attache.

Michael Lanyard, aka the Lone Wolf, is sailing to America when he meets pretty Eve de Montalais. Eve wants to sneak her valuable necklace through U.S. customs so that she can use the money from its sale to help straighten out her brother. The only problem is that there is a gang of jewel thieves on board who are just as determined to steal the necklace.

The Lone Wolf, an international thief who is expert in dodging the police, is rifling a wall safe when he senses the approach of detectives. Secreting a necklace in a cigarette case, he makes a hasty retreat. In disguise, he climbs to the balcony of another house where a bal masque is in progress and conceals himself in Marcia Mayfair's boudoir. Later he mingles with the guests and dances with Marcia. Lanyard is disclosed as a stranger when detectives force the guests to unmask, but Marcia remains silent while Lanyard replaces the jewels lifted from her bedroom. Lanyard is warned by Detective Crane, who suspects him but has no evidence. A visit to a bohemian resort owned by Morphew, leader of a band of thieves, provokes a heated argument in which Lanyard is threatened; and Marcia and Lanyard barely escape being caught in a raid. Their romance is threatened when Marcia's jewels are again stolen, but Lanyard traps Morphew and his gang and brings them to justice.

When Marcel, a waif, saves master crook Burke from the police, Burke adopts the youngster and teaches him his profession. Years later, Marcel has become a master crook himself, working under the name of Michael Lanyard. His clever work baffles the Paris police, who dub him "The Lone Wolf". The Pack, a gang of criminals, notifies The Wolf that unless he joins them, he is marked for destruction. Lucy, an undercover agent masquerading as a crook to expose the gang, helps The Wolf escape. This inaugurates a series of adventures in which Lucy and The Wolf are pursued by the gang, finally making their escape to England by plane. The Pack follows, only to meet their death in a plane crash. Liberated from his tormentors, The Wolf vows to go straight and marries Lucy.