Yu Tong, a fire investigator with the Qingdu City Fire Brigade, faces a perplexing case of spontaneous combustion in a lake on his very first assignment. His exceptional skills quickly catch the attention of the brilliant detective Lin Yaoyao. Despite their contrasting personalities, they must work together to unravel a series of mysterious fire incidents. As they delve deeper into the investigation, hidden layers of Yu Tong's character emerge, and an old case from his past resurfaces, leading to shocking revelations that will challenge everything they thought they knew.