Boris Karloff was originally hired to play John F. Black but it soon became clear that his severe arthritis would not permit him to undertake such a strenuous role. Karloff was switched to the part of Mr. Hinchley, and Basil Rathbone was brought in to play Black.
In Spain hadn't a theatrical release until 1984, 21 years later. The film was only released -with 1 copy- at first in Barcelona (February/84, Maryland) and later in Madrid (May/84, Bellas Artes), only projected in subtitled version. The dubbed version was for VHS premiere (1984) and later was broadcast on TV premiere.