The Warning 1927

This story of the British Silent Service operating on the coast of China finds Tom Fellows, captain of an opium-smuggling ship, going into a notorious Chinese joint called "The House of a Thousand Delights," where he finds a beautiful girl, Mary Blake, bound and captive. He starts a brawl, rescues Mary in the mêlée that follows, and then loses her when she flees to a hotel. He follows her and finds she is mixed up in some mysterious activity. However, he knows more about her than she does him (because he isn't what he is supposed to be - and she isn't, either), he stays close by, even to the point of using a machine-gun to dispel a mob at a Chinese temple.