In the depths of the London subway system, darkness is more than just a mere gloomy backdrop; it conceals an atrocious secret. A group of students dares to explore an abandoned stretch and stumbles upon a series of strange disappearances that have unsettled the city. When one of the students goes missing, his friends, determined to find him, begin to investigate and uncover a terrifying legend: a man, the result of a failed experiment, has been living in the depths of the subway since wartime, becoming a cannibal that preys on those who venture too close to his territory.
Meanwhile, the police, skeptical of horror stories, start investigating the series of inexplicable events surrounding the missing persons. As tension rises, a pragmatic inspector and an agent more accustomed to the horrors of the streets comb through the subway, confronting a chilling truth that defies all logic: the monster of the tale is real and dwells in an environment the world has forgotten.
With an unsettling atmosphere and a touch of social satire, the protagonists soon find themselves in a race against time to save their friend and stop the monster before it's too late. The darkness of the subway becomes a battleground between reason and primal horror, where what lurks in the shadows is far more terrifying than they ever imagined.