A British anthropologist, Sir Alexander Saxton (Christopher Lee), discovers a frozen primitive ape-man in Manchuria, China, and ships it back on the TranSiberian train he's taking. But there's something alive inside the frozen corpse--and it begins to suck out the energy out of the passengers. It taks all of their memories. Basically, the "Being" that's possessing people is an alien, who has been existing this way for millions of years. There's a Pseudo-religious aspect to this (it may be the devil), with there being this crazy priest on board. Eventually it takes over the majority of the passengers on the train, including Tellly Savalas, who all look like white-eyed zombies.