A professional guide led seven mountaineers trespassing the rarely known secret area of Huadong Mountain. Five of them died differently, and their bodies are found in the wild jungle; one of them is still missing; and the only survivor is an autism patient who refuses to talk about it. The only remaining clue to the case is a digital voice recorder.

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Relying on the voice recorder, the police make a painstaking investigation. However, it is bewildering that there was a snowstorm in an altitude where snow is impossible. The snowstorm drove the seven of them to a cave for shelter, and also trapped them at 23:59 forever.

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There is a mysterious man who is not on the investigation list appears in the cave and there is a line written in blood saying “The dawn will come only when the secret is revealed” on the cave wall.

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Adversity brings out the dark side of humanity. The eight of them, each with an unspeakable secret, kill each other in the inescapable darkness. What is the real truth about this accident?