Charles Regnier is the author of 'Fraudulent Justice' which looks to become a bestseller. But it is potentially an embarrassment to the French Government. A man is carrying some secrets documents from the Archives of the Ministry of Justice when he is killed. His body has been clawed to ribbons as though he had been attacked by a powerful cat. The documents he was carrying go missing so it would seem that the murderer didn't want those papers scrutinized for some reason.

Suspicion falls upon Regnier as he was unaccountably out all night at the time of the murder. He is in the habit of leaving social gatherings on his own complaining of a headache. He sees visions of a storm and then the sight of a black cat appears. He seems to be suffering from amnesia brought on by a tropical fever he had contracted on his travels. He is accused of learning secret rituals he has discovered in India and Tibet.

A favorite of a number of 1940s B-mystery fans Douglass Dumbrille portrays the friend of Charles Regnier. There is a very good horse and carriage chase sequence but a confusing fight scene earlier in a cafe had been poorly executed. This is a reasonable mystery involving transmutation that has number of atmospheric moments. And the reproduction poster for this film with the killer's blue hand threatening the neck of a beautiful female victim has become collectible among horror film poster fans.