- Devastated over his girlfriend's death in a traffic accident, psychologist Chung Tai Yin (Kenneth Ma) has spent five years to seek the truth. The psychological assessment of a campus murder suspect, Lo Kin Keung (Willie Wai), conducted by his late girlfriend showed that Kin Keung lacked a murder motive and had no violent tendency. During Tai Yin's investigation, he encounters a prodigy named Tung Yat (Mat Yeung) who has Asperger's syndrome, and his younger sister Tung Yuet (Sisley Choi). Tung Yat is socially awkward and often brings trouble to his sister. Many years ago, he even caused police officer Wu Tin Yeung (Pierre Ngo) to fail in his undercover operation. However, due to Tai Yin, all of them gradually become good friends, and they even help him hunt down the culprit. Out of the blue, a person involved in the case, Wong Hoi Ching (Grace Wong), whom they have had no contact with for many years, show up and visits Kin Keung in jail, drastically changing the case...