When registered clinical psychologist CHUNG TAI-YIN is driving on the highway, he recalls the past and cannot help tearing up. For research, TAI-YIN interviewed a murderer LO KIN-KEUNG a year ago. KIN-KEUNG is extremely sensitive. TAI-YIN adopts every possible way to try to trigger his memory of the murder, but to no avail. Upon TAI-YIN's return home, his girlfriend, TSANG SAU-YEE who is also a psychologist, asks him about his opinion after the interview. TAI-YIN does not believe that KIN-KEUNG would ever hurt anyone, so he is determined to solve the mystery. There is a virus in the computers of the company that TUNG YAT works for, so his boss immediately tells him to fix the problem. However, TUNG YAT's response makes his boss so angry that he yells at him. TUNG YAT's sister, TUNG YUET, is a social worker. She accompanies TUNG YAT to the police station, during which she keeps reprimanding him, hoping him to understand the seriousness of the consequence. With TUNG YAT appearing at court, the judge, who is aware of his problem, makes a compulsory psychiatric treatment order. TUNG YUET seeks help from TAI-YIN, but TUNG YAT walks to TAI-YIN's office and frankly tells him that he did not want to come. TAI-YIN suggests that he does not have to come as long as he promises to do one thing for him. Having heard this, TUNG YAT becomes very happy and agrees. TAI-YIN finds TUNG YAT's case is very interesting, and wants to help him because he notices that TUNG YAT has a very high IQ. CHAN MEI-YAN comes to meet TAI-YIN and reveals her ex-husband LEUNG CHI-FUNG's situation to TAI-YIN, who immediately goes to probe into the matter.

With the door bell ringing, CHI-FUNG goes to open the door and sees the police. TIN-YEUNG comes forward and reveals his identity, alleging that CHI-FUNG's oldest son, WAI-SHUN, is suspected in a murder. Upon TUNG YUET's return home, TUNG YAT tells her that he met a very smart kid, unfortunately, no one understood him except TUNG YAT himself. TAI-YIN arrives at CHI-FUNG's home and sees that TUNG YAT is doing mathematics with CHI-FUNG's youngest son, WAI-CHUNG. After listening to what CHI-FUNG said, he finds out that WAI-SHUN seems to be socially awkward which might stem from family problems. In order to look for WAI-SHUN, CHI-FUNG intends to temporarily arrange for WAI-CHUNG to stay in an orphanage, but WAI-CHUNG refuses. TAI-YIN goes to a restaurant to look for HAU-MAN after learning that it's her birthday. Seeing that she is dating a married man, he cannot help driving him away. Meanwhile, TIN-YEUNG enters a country house to investigate the case, only to find out that TUNG YAT is there too.

To investigate KIN-KEUNG's case, TAI-YIN takes the initiative to contact the victims' family members, asking them whether anyone among the three victims was dating anyone. TAI-YIN conducts an analysis and rules out the possibility that KIN-KEUNG killed them due to the breakdown of his relationship with them. MEI-YAN asks TAI-YIN whether he agrees to be the witness for the child custody case, instead TAI-YIN asks whether CHI-FUNG is not WAI-CHUNG's biological father. TAI-YIN returns to the clinic only to find that TUNG YAT and TIN-YEUNG are together so he cannot help feeling strange. HAU-MAN is poured paint on by a married man's wife, which leaves her no other choice but to go to TAI-YIN's home to wash her clothes. Seeing that TAI-YIN makes his study room look like SAU-YEE's office, HAU-MAN becomes very angry. CHI-FUNG bursts into TAI-YIN's office, accusing him of helping MEI-YAN separate him and WAI-CHUNG. After CHI-FUNG goes together with WAI-CHUNG back to the orphanage, he goes to meet up with WAI-SHUN in secret. He then asks WAI-SHUN what happened, so WAI-SHUN tells him the whole thing.

TUNG YUET goes to meet TAI-YIN, telling him CHI-FUNG has gone missing. The police even take TUNG YAT into custody as they suspect that he is involved in the murder case. According to TAI-YIN, CHI-FUNG and his two sons have all gone missing. CHI-FUNG arrives at the park to meet WAI-CHUNG, asking him why he left the orphanage. He arranges for WAI-SHUN to take a boat to leave Hong Kong, but they later run into the police. With MEI-YAN noticing that WAI-CHUNG carries CHI-FUNG's confession letter, TAI-YIN urges TIN-YEUNG to look for CHI-FUNG, fearing that CHI-FUNG is going to kill himself. After the police arrest WAI-SHUN, TIN-YEUNG takes the statement from him, and learns that he is not the killer. TAI-YIN locates the address where CHI-FUNG is hiding, so he immediately informs TIN-YEUNG to rush there and save him. TIN-YEUNG meets up with TAI-YIN, hoping that he can help analyze who is the culprit. Ever since TUNG YAT saved CHI-FUNG, he has become a hero and many reporters want to interview him.

TIN-YEUNG arrests TUNG YAT, accusing him of computer fraud. When TUNG YUET and TUNG YAT leave the police station, TUNG YUET laments that no lawyer is willing to defend TUNG YAT. TAI-YIN feels that TIN-YEUNG not only picks on TUNG YAT, but also hates his guts, so he asks TUNG YUET to help probe into the matter, wondering whether TUNG YAT offended TIN-YEUNG in the past. Once again, TAI-YIN goes to visit KIN-KEUNG, following which he hands KIN-KEUNG's favorite articles to HAU-MAN. The two then start discussing that KIN-KEUNG went with the victims to a place that was covered by snow. HOI-CHING finds TUNG YAT and reveals her intention, which is to invite him on an internet radio show. However, TUNG YAT abruptly turns her down. After HOI-CHING lets TUNG YAT listen to TIN-YEUNG's audio recordings, TUNG YAT claims that the situation was not like TIN-YEUNG described, adding that he wants TIN-YEUNG to apologize. Hearing that TUNG YAT mentioned about the female host whose name is HOI-CHING, TAI-YIN instantly recalls that she was involved in KIN-KEUNG's case. Therefore, he suggests that TUNG YAT should attend the internet radio show to explain the whole thing.

Upon TUNG YUET's return home, she sees TUNG YAT stand at the edge of the rooftop terrace, and right away she dashes there to save him. TUNG YUET questions HANA whether she induced TUNG YAT to take any drugs, to which HANA denies, saying that the drug was stolen. TUNG YUET analyzes the situation and concludes that HANA's brother MAN attempted to give HANA the drug, but was discovered by their mother PING, who threw away the drug. TAI-YIN arranges for TUNG YAT to have a dinner with TIN-YEUNG, hoping that TUNG YAT can learn how to get along with the others. With TIN-YEUNG noticing a girl suffer severe injuries, the police investigate and find that she is a street dancer. Through their investigation, TIN-YEUNG learns from other youth that TUNG YUET is the social worker who helps HANA. At the police station, TIN-YEUNG bumps into TUNG YUET, he immediately tells her about what happened to NGAR-YEE. TAI-YIN becomes the guest host for the radio station, during which YU KIN asks his opinion about the murder case. TAI-YIN out of the blue claims that HOI-CHING is the sole survivor of the murder.