A traffic accident occurrs on the highway. A bus, carries 31 passengers, breaks off the road and plungs into a river valley with only 6 passengers are alive.

After hiding on the roof of the bus all night, the remaining four encounter another flood. The flood recedes, and the four finally waits the call from rescuers.

While Li Qiao proposing to go to the upstream to find a way out, Lu Min insists on going downstream to investigate the alarm.

Li Qiao is able to recognize Chen Jian because she finds an off-road vehicle when she goes upstream to find a way out.

Li Qiao is convinced that Chen Jian keeps a secret from them and asks to keep him at the bottom of the well. She also finds Ma Hongxin's body.

Zou Zhiming and others pretend to believe in Chen Jian and follow him to the downstream. However, unexpected changes occurr on the way.