Eugenio Martin directs this sci-fi horror starring Christopher Lee, Peter Cushing and Telly Savalas. Professor Alexander Saxton (Lee) believes that he has found the missing link in human evolution in the form of a frozen ape-like creature. He has it transported on the Trans Siberian Express but his rival, Doctor Wells (Cushing), is unconvinced of the beast's origins. His suspicions appear to be confirmed when passengers on the train begin to die mysteriously, the victims of an evil force that had been buried with the ape.