Many people have the superpower of seeing something invisible. Jia Kai can't see ghosts, but he can see the different colored threads connecting people. The more threads, the more bonds a person has.
Jia Kai has seen countless threads, but he hasn't been connected to anyone at all. He can't figure out why but has accepted himself as a loner. However, because of a chaotic incident, he meets a policeman named Da Wei and realizes that one silver-grey thread has grown from him to him, connecting them together!
Jia Kai doesn't want to lose the connection, so he takes a part-time job at the police station to get closer to Da Wei. With his superpower, he helps with cases of missing people and objects. They get to know each other better, and the thread between them begins to change color, from silver-grey to yellow, representing friendship, and even to red, representing love. Seeing these changes, Jia Kai realizes that how they feel for each other can't be hidden anymore...