A teenage loner pushes his way into the underworld of a high school crime ring to investigate the disappearance of his ex-girlfriend.

A hardworking secretary for a rich woman finds herself engaged to the woman's son and accused of a murder she didn't commit.

Michael Lanyard is suspected of stealing two fabulous diamonds from a vault in Scotland Yard, where they were being held for safekeeping, but the Yard can't prove he did it. Later, Lanyard is summoned by a member of the nobility to help the latter raise money to pay a blackmailer. Lanyard later finds evidence to reveal the diamonds as having been stolen by a famous stage star.

Michael Lanyard's faithful butler Jamison is mistaken for his boss by a gang of jewel robbers.

Complicated plot involving missing stamp collection and kidnapped businessman, with the Lone Wolf keeping one step ahead of the police in Havana trying to solve the crime and make a profit.

Spies force former jewel thief Michael Lanyard to steal defense secrets in Washington.

Reformed jewel thief the Lone Wolf investigates the murder of a playboy who was blackmailing three socialites.

The Lone Wolf tracks down Nazi spies in London during the German bombing.

Former jewel thief Michael Lanyard toys with a princess and a grand duke.

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.

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.

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.