With Alfred Hitchcock recently gone to Hollywood, Michael Powell shot a comedy-thriller in the master's style. The MacGuffin loosely draws on the war. A Danish merchant seaman (Conrad Veidt) is hauled into port to have his cargo inspected by customs. Then he follows his wilful, enigmatic passenger (Valerie Hobson) into a London full of German spies.
Naturally, she is working undercover for the British. And after they have worn each other out by squabbling, they fall in love. Veidt and Hobson were re-united following their 1939 hit, The Spy in Black. Veidt is a convincing sea captain, but not so much a romantic lead. Hobson is more comfortable with the romcom froth. Including a startling bondage scene.
The episodic spy story is a means to get the stars from one mysterious cliffhanger to another while they get to know each other over the long dark night. The comedy works better than the suspense, with the typically terse, tight lipped exchanges of the period. It is set in a blackout in the London fog which gives the film plenty of noirish atmosphere.
Hay Petrie is a bonus in a dual role as a sailor/restaurant owner. This is not as good as The Spy in Black, or Hitchcock's similar WWII espionage films. But the stars have a comic rapport, even if not credible as lovers. It looks like it was made quickly on a small budget, but it was a funny and entertaining diversion from the realities of the home front.