Blackout

... from British National Films and director Michael Powell. Danish merchant ship's Captain Andersen (Conrad Veidt) is irritated enough when his ship is ordered into dock for inspection for contraband by British authorities. It only gets worse when two passengers, Mrs. Sorensen (Valeriea Hobson) and Mr. Pidgeon (Esmond Knight), sneak off the ship. Captain Andersen tracks them down through the darkness of London in an enforced blackout, only to end up targeted by a Nazi spy ring.

There's a light-heartedness that runs through this entertaining thriller. Veidt, cast against type, is good as the put-upon ship's captain that just wants to get back home. Hobson is excellent as the mysterious Mrs. Sorensen. Some of the comic relief bits with Hay Petrie in a dual role can get a bit long, but it's not too awful. Contraband was the original British release title, which was changed to Blackout for the US market, as well as having 12 minutes shaved off the running time.