In 1906 Shanghai, anthropologist Professor Sir Alexander Saxton, portrayed by the legendary Christopher Lee, is making his way back to England aboard the Trans-Siberian Railway, with an intriguing prize from his expedition in the mountains of Manchuria. He has in his possession a sizable crate that contains what he believes could be the missing link in human evolution—the frozen remains of a primitive humanoid creature. Accompanying him is his colleague from the Geological Society of London, Dr. Wells, acted by the iconic Peter Cushing.
Before the train even departs, a wave of mystery and treachery unfolds. A notorious thief ends up dead on the platform after peering into the enigmatic crate, his lifeless body horrifyingly found with bleeding eyes, now blank and white. Enter Pujardov, a monk reminiscent of Rasputin, who claims that the crate harbors evil. Serving as the spiritual adviser to Count Maryan Petrovski (played by George Rigaud) and his wife Irina (portrayed by Silvia Tortosa), he asserts that the crate is a harbinger of doom based on a peculiar interpretation of the cross—a chalk mark fails to make an impression on the side of the crate. Despite Pujardov's warning, Saxton takes him lightly, dismissing him as a mere trickster.
Desperately wishing to keep his remarkable find hidden, Saxton is dismayed when Wells bribes the baggage handler (José Jaspe) to reveal the secret within the crate. However, the revelation is fatal—a glowing red-eyed creature emerges, claiming another victim as it drains the life force from the unsuspecting handler. As the train rattles toward Moscow, the creature wreaks havoc, eventually causing Inspector Mirov, a figure of authority on the train, to suppress the news of the creeping dread among the passengers while initiating a search for the elusive beast.
In a twist of events, a captivating woman named Natasha (played by Helga Liné) ingratiates herself into Wells' compartment, pretending to be in dire straits. But her true intention is far more sinister, for she’s a spy determined to steal a block of steel belonging to the Count—a secret known only to him. Her true identity is jeopardized when she is spotted by Yevtushenko (played by Ángel del Pozo), an engineer who recognizes her.
When Wells and his assistant, Miss Jones, conduct an autopsy on the baggage handler, they discover an alarming insight—his brain is unnaturally smooth, leading to the unsettling conclusion that it has been abstracted of all memories and knowledge. This grotesque realization unveils the creature’s unfathomable nature as it stalks the train, further victimizing the unwitting passengers.
Ultimately, a raging battle pits Saxton, Wells, and the surviving passengers against an increasingly ominous threat. The creature's malevolent force transfers to individuals, culminating in chaos as the train nears its end. With the train inevitably collapsing over a cliff, a blaze engulfs it, leaving the survivors in awe of the fallout—a conclusion capturing the essence of horror, adventure, and the relentless pursuit of knowledge, as they witness the flames consuming not just the train, but some otherworldly entities that sought to prey upon them.
