In the early 1900s, flooding and drowning happened often in Tianjin (Tientsin). But when a local shipping magnate was found dead at the bottom of a river, he was chained to a statue and had drowned. Guo De You, the captain of the police department's underwater recovery team, was the main suspect because he was the only person in the city who could stay underwater long enough to do the job. Ding Mao, the businessman's son, tried to prove that Guo was guilty, but his own forensic discovery and a strange drowning in the same area made him question his first opinion. Together with spirit medium Gu Ying and news reporter Xiao Lan Lan, they peeled back the layers of the mystery and found that the clues pointed to an event that happened over 20 years ago, when an evil cult was destroying the city. Now, the cult was making trouble again. To stop them from coming back, the team must look into the strange, unexplained things that happened in their city.