Ray Milland is in studio records for the role of "Forbes", but he did not appear in the movie.
Philip MacDonald's novel was first published in London as "X v. Rex" using his pseudonym, Martin Porlock. It was published in America as "The Mystery of the Dead Police" under his real name.
Preview audiences rejected the original ending, where "Nick" did not get "Jane". Retakes and additional scenes were ordered, but directed by Richard Boleslawski because director Edgar Selwyn was unavailable.