In 1906, Saxton (Lee), a renowned British anthropologist, is returning to Europe by the Trans-Siberian Express from China to Moscow. With him is a crate containing the frozen remains of a primitive humanoid creature that he discovered in a cave in Manchuria. He hopes it is a missing link in human evolution. Doctor Wells (Peter Cushing), Saxton's friendly rival and Royal Geological Society colleague, is also on board but travelling separately. Before the train departs Shanghai, a thief is found dead on the platform. His eyes are completely white, without irises or pupils, and a bystander initially mistakes him for a blind man. The Polish Count Marion Petrovski (George Rigaud) and Countess Irina Petrovski (Silvia Tortosa) are also waiting to board the train with their spiritual advisor, an Eastern Orthodox monk named Father Pujardov (Alberto de Mendoza), who proclaims the contents of the crate to be evil. Saxton furiously dismisses this as superstition. Saxton's eagerness to keep his scientific find secret arouses the suspicion of Wells, who bribes a porter to investigate the crate. The porter is killed by the defrosted humanoid (Juan Olaguivel) within. It then escapes the crate by picking the lock.