A series of explosions mirror a past case, prompting a joint investigation between SWAT and Criminal Investigation Bureau.

The whole town is waiting for the "flood dragon" to transform into a true dragon, yet no one realizes someone is waiting for a sacrifice! Rain pours relentlessly for seven days, and strange deaths occur one after another… Taoist Zhang Buping arrives in Longkou Town and discovers that every victim bears an ominous "Fallen Dragon Claw" mark. Is this the fulfillment of a thousand-year-old legend, or the perfect crime of killing in the name of a god?

In the 1990s, two police officers ventured into the mountains along Zhejiang's Shanxi Stream to track down a suspect from an old case. As they dug deeper into the past, long-buried memories resurfaced, stirring poignant recollections among everyone involved about Zhang Xue, the person who had gone missing.