Officer 666 (1920)

Learning the notorious art thief Alf Wilson plans to steal his valuable paintings, idle millionaire Travers Gladwyn decides to amuse himself by guarding his own home. After bribing Policeman Phelan, Officer 666, with a $500 bill, Travers dons the officer's uniform and identity. When Wilson appears at his mansion, Travers questions him and discovers that Wilson is posing as Travers, claiming that he is packing up his paintings for safe keeping. Then Helen Barton, who has promised to elope with Wilson, arrives, assuming that she is in the Wilson home. Travers, who has fallen in love with Helen, is agitated by this, and so reveals his true identity and summons Phelan. Wilson matches wits against the millionaire by attempting to convince the officer that the $500 bill is counterfeit. When the police arrive, both men claim to be Travers Gladwyn until a detective, intent on arresting Wilson for the kidnapping of Helen Barton, appears and identifies the real crook. The situation thus clarified, Travers wins Helen.