Introduction: While the city is dredging a riverbed, human remains are unearthed. Medical examiner Qin Ming discovers that the victim is a woman from an old case years ago. On Qin Ming's birthday, sunspot activity causes his toy walkie-talkie to connect with his father, Qin Tian, 30 years in the past. Qin Ming warns Qin Tian about an explosion and saves him, but this triggers the Rainy Night Hammer Killer serial case. Two generations of police officers work together across time to solve the case and uncover the truth.