A professional guide leads a group of seven hikers to explore a rare and secret area in the mountainous part of Hualien and Taitung. Five of them die, all with different causes of death, leaving a trail of corpses in the mountains. There is one person still missing. The only survivor is an autistic person who is unwilling to testify. The only remaining clue to solve the case is a recording pen.
The police launch a painstaking investigation of the case relying on the content of the recorder pen. But what's strange about this case is that an unusual snowstorm fell in this low-altitude area and drove the seven people into a cave to find shelter. And it was this snowstorm that trapped them in the never-ending darkness.
In the cave where the hikers seek refuge, there is a mysterious eighth person whose identity is not known to the criminal investigators. On the wall deep inside the cave, there is a message written in blood: "The dawn comes only after the secret has been revealed."
Eight people, each harboring a secret they cannot reveal, kill each other in the darkness of the night. Do you think you can find out the truth from the clues left at the crime scene?
An autistic person who is also the younger twin brother. He finds it difficult to communicate with people and is only interested in mountains. His psychiatrist once encouraged him to use a tape recorder to record what he sees, feels, and thinks. Since then he carries a recording device with him every day, which has slowly made him able to go out and talk to people. After he joined a hiking group, he found there is a girl he likes.
The elder twin brother, whose personality is the opposite of his brother. He is optimistic, and from a young age, he has had excellent grades and athleticism, making him very popular. He always tries to look after his young brother, but in his heart, he looks down on him.
The person that Chang Chia-yü secretly likes from the hiking group. She is also Chang Chia-hsiang's girlfriend. She once had an affair with a married man in another hiking group.