Algy, in the person of John Newland, has purchased a model ship by accident at auction. June Vincent wants it and is willing to buy it at a profit, but Tom Conway as Bulldog Drummond, saunters through the movie trying to figure out why.
It's definitely a Bulldog Drummond story, being based on a story by 'Sapper'. It's also a pretty good mystery. However, its relationship to the series of stories written by Herman C. McNeile is problematic. When he first showed up, Drummond was a gorilla of a man with extensive scarring from service in the Great War. That didn't last long; the first movie Bulldog was Carlyle Blackwell in 1922, and he was subsequently played by people like Ronald Colman and John Howard. Conway plays this like George Sanders' brother, which he was. Good thing the mystery is difficult to figure out.