The Lone Wolf Strikes

Phillip Jordan offers Weldon the use of his valuable pearl necklace for her birthday. Weldon swaps it for a convincing imitation and gives the real necklace to her boyfriend, Jim Ryder. When Jordan breaks the necklace, a jeweler detects the forgery and trouble begins.

Jordan telephones Weldon to say he will come to collect the real necklace. Ryder instead arranges a fatal car crash to cover the theft and to claim the piece for himself.

Stanley Young asks his friend Michael Lanyard, the Lone Wolf, to help recover the necklace. Lanyard owes Young a big favor and agrees to take the case, while his bored valet Jamison looks on with interest.

Delia, Phillip Jordan's daughter, meets Ralph Bolton on a sea voyage and is charmed by him. Bolton is a crook who reports to his boss Alberts that Lanyard is involved, while Alberts remains confident that Lanyard will retrieve the necklace before taking it himself.

Lanyard learns that Ryder plans to sell the pearls to his old friend Emil Gorlick. Delia tails Lanyard to Gorlick's hotel and watches as he confirms Gorlick will see Weldon and Ryder that night.

Lanyard incapacitates Gorlick and takes his place in the hotel room, moving to intercept the planned meeting between Gorlick, Weldon, and Ryder.

Delia peeps through a keyhole to glimpse Lanyard's plan. The hotel detective unmasks her, frees Gorlick, and Delia flees in a taxi as Gorlick joins the chase with a pistol.

Lanyard succeeds in taking the real necklace before Gorlick arrives and hands it to Stanley Young, who, as a joke, gifts him the fake as a memento.

Young makes the mistake of informing Bolton that the pearls have been recovered, prompting Bolton to report to Alberts and reassess the situation.

Ryder calls Lanyard demanding the necklace for Delia. To keep things moving, Lanyard gives the thieves the fake and keeps the real pearls out of sight.

Lanyard explains the situation to Delia and they go to Young's place, only to find him dead and the pearls missing. The mystery deepens as the real treasure seems to have slipped away again.

Alberts' gang goes to the Jordan mansion. Lanyard appears, pretends to have the pearls, and leads them on a car chase to a ferry, with Jamison driving aboard as police close in.

The ferry sails with the police in pursuit and the crooks trapped. Lanyard's ruse seals their fate as the pearls remain out of reach for the criminals.