Apart from that special gift, Chang Yi-hsien is just an ordinary university student.
In his eyes, everyone has strings in various colors attached that connect them to others. The colors of the strings reflect their feelings such as romance, family love, friendship or appreciation for things. Although Yi-hsien can see all these strings, he has none attached to himself. Hence, he believes that he himself is incapable of having feelings. Nevertheless, his kindness always prompts him to save those who have lost all the strings attached, i.e., people who might commit suicide.
One day when Yi-hsien tries to stop an old man from killing himself, he is sent to the police. A police officer named Huang Shih-hung calls out to him. It turns out that a few weeks ago, Yi-hsien was on another suicide scene when it was reported, and this makes Shih-hung curious about how Yi-hsien could coincidentally stop two suicide attempts.
While being questioned, Yi-hsien suddenly catches sight of a string connecting Shih-hung and himself, and it is in silver-grey, a color that he has never seen before! When Yi-hsien returns home, he cannot stop thinking about Shih-hung. Having had no strings attached to himself for 20 years, Yi-hsien really wants to know what that unique silver-grey thread means.
Yi-hsien approach Shih-hung to find the answer, and during the process, he helps the police solve several cases with his gift. In one conflict, however, Yi-hsien’s memory of his unexplained fear of fire is awakened. Later Shih-hung admits that he lost some memories due to an accident in his childhood.
Shih-hung believes that his lost memories are the key to the string connecting them. As they investigate further, they discover that Shih-hung’s parents did not die in a car accident but a tragedy that involved two families – a violent husband pursued his runaway wife and set fire to the childminder’s home.
In the end, only the childminder’s son and the couple’s son, a victim of domestic abuse, survived the arson attack. Both the loss of Shih-hung’s memories and the special gift Yi-hsien gained stemmed from the shock of witnessing the accident. Yi-hsien is so stunned by this discovery that he loses his ability to see the strings.
Later a serious domestic violence case is reported, in which a child has gone missing. The similar situation gives Yi-hsien such a strong sense of déjà vu that he remembers in his childhood, he always hid in his “secret base” when his father got angry. This not only gives Yi-hsien a clue to find the missing child but reminds him of his mother’s love that he had long forgotten. For the first time in his life, he wails out loud as if the child before him were his younger self.
Yi-hsien regains the ability to see the strings! Now Yi-hsien is no different from others; he is no longer fearful. He just wants to see Shih-hung again and the thread that connects them. At first, it is silver-grey; soon, it turns beige and then yellow, and now, it is shimmering pink!