For as long as crime boss Albert Mendoza (Everett Sloane) has been running a notorious ring of hired hit men, District Attorney Martin Ferguson (Humphrey Bogart) has been hunting him down. But Ferguson cuts a deal with Mendoza's henchman Joe Rico (Ted De Corsia), and the mob boss is finally arrested. However, Rico dies mysteriously before he can testify against Mendoza.

In 1906 on a train racing through Siberia, mysterious and unearthly deaths start to occur while Professor Saxton is transporting the frozen remains of a primitive humanoid creature he found in Manchuria back to Europe.