“(Producer Alexander) Korda brought Powell and Pressburger together for the first time to devise a subject worthy of the autocratic Conrad Veidt. He plays a World War I U-boat captain who comes ashore at Scapa Flow to collect naval secrets from a German spy, but instead enters a well-prepared trap. The night scenes are remarkable, while Pressburger's concern with dramatic paradox is already evident in the relationship between Veidt and ‘Mrs. Ashington,' and in the reversals of duty and deceit.” -British Film Institute.

“One of a number of films made on the threshold of WW II, which seemed to say that if war came, there was no reason why it couldn't be conducted along the gentlemanly lines of certain aspects of the previous war. Of course, this largely depended on one's opponent turning out to be like Conrad Veidt! Spy In Black is one of the best of the earlier Powell thrillers, casting visual echoes from Nosferatu, using a fine (early) score by Miklos Rosza, and mixing studio work with well-chosen locations in the manner of so many later Powell films.”