Doubling with Danger (1926)

While Elwood Haver is visiting an inventor who is working on a special airplane for the government, the inventor is killed and Haver guards his papers carefully. Retiring to his country mansion, Haver puts himself under the protection of eccentric detective Avery McCade. At a house party, Malcolm Davis and Arthur Channing are among the guests; the latter romances Madeline, Haver's daughter, but to no avail. McCade accuses his secretary, Dick, of being a criminal, but Dick explains that he has a twin brother whom he himself brought to justice; Haver, disbelieving him, dispenses with his services. Overhearing Channing and a servant arranging a meeting, Dick follows them, assumes the role of his twin brother, and is engaged to steal the papers from Haver. He succeeds in acquiring the papers, but he will not surrender them until he is paid; Madeline is abducted, but following a series of fights and chases, Dick, Haver, and McCade capture the crooks.