Qiandao Lake rookie search and rescue officer Yu Zaishui is looking for a boat that was washed into the lake by the flood. With the help of retired search and rescue officer Hu Xunzhou, Yu realises that the case is related to a missing old man. The floodgate at Qiandao Lake is about to open and they must find him before that happens. During the operation, the Xin’an River Great Migration incident from 60 years ago emerges…