As the hiking club reunion gets underway, a text message from the mysteriously absent host Xinyi breaks the awkward atmosphere.

With no way to escape or communicate with the outside world, the group is forced to fend for itself and deal with an explosive secret.

As yet another victim falls, Awei reveals a shocking bit of news that may shed light on the incident from a decade ago.

The remaining vacationers wake to discover their circumstances have dramatically changed. Later, the group makes a discovery.

As another body emerges, everyone begins to point fingers at one another. Later, the official investigation begins.

While Yazheng analyzes each person's testimony, clues -- and a theory -- gradually begin to emerge