Wolfson and George Oppenheimer was based on The Blonde Countess, a 1933 novel by Herbert Yardley, founder and head of the Black Chamber, as adapted by Bella and Samuel Spewack.

The couple spend the day together where Gordon confides that because he once wrote a book on cryptography under a pen name, the army is searching for him to put him to work behind a desk, but he is eager to get into the fighting.

Over his objections, Carter assigns Gordon to the code-breaking room to help break an intercepted German message that Major Brennan (Lionel Atwill), an experienced British cryptologist, has been unable to decipher.

However a German spy ring in the city has already gained access to the code and allows the ship through to lure more valuable troop transports into their U-boat trap.

Although he has a circular mailed to Olivia that contains a message written in invisible ink, and has her brought in for questioning, Gordon releases her to lead him to the rest of the spies.

Olivia covertly warns Captain Nicholas Nieterstein (Cesar Romero), an attaché in a foreign embassy who is part of the spy ring, that the Americans have the circular, which requires use of a reagent to reveal the message.

Olivia is told that the spy ring is going to betray Nieterstein to dupe the Americans into transmitting the rendezvous location to the troop convoy.

Dining later with Gordon, Olivia "accidentally" drops one of Nieterstein's military medals in her possession into a glass of water, revealing the reagent and his complicity.

It was shot in five weeks from June 24 to July 29, 1935, although production was suspended for a time due to an attack of appendicitis suffered by Binnie Barnes.

[1] When it was reported in the press that the studio was going to scrap the picture and rewrite and reshoot it, director William K. Howard responded that, in fact, they were only concerned about the ending of the film, which had been unsatisfactory from the beginning.

Cinematographer William H. Daniels also left: they were replaced by Sam Wood and James Wong Howe, respectively, neither of whom received credit for their work.

"[5] In 1942, the story was updated to World War II and filmed as Pacific Rendezvous with Lee Bowman and Jean Rogers in the Powell and Russell roles.