Jack Banning, a Secret Service operative, is assigned to thwart the activities of a gang of silk smugglers. Disguised as a motorcycle officer, Banning patrols their rendezvous by day, and at night he poses as a crook, "Strongarm Samson." He soon is attracted to Marion Macy, a banker's daughter, also sought after by Courtney, who heads the smugglers; but she recognizes him and informs Courtney that he is a policeman. Banning is captured by Courtney's henchman, Spanish Joe, but escapes; Marion is lured to the hideout, and Dorina, also an undercover agent, awaits the officers while Banning returns to rescue Marion from Courtney's clutches after a desperate battle. The smugglers are captured, and Banning is united with Marion.