LAI goes out for dinner with ON and his family, during which an acid-filled bottle suddenly falls onto the street and injures a number of pedestrians. HEI attends an admission interview with an elite school. Although he has made quite an impression on the principal, he is not selected in the end because of his parents’ poor performance. LEUNG finally manages to convince LAI to consult POK for him, although POK has turned him down already some time earlier. A conference has been postponed, so POK can find time to help LEUNG. He suggests conducting a series of experiments to collect more data, but would need an assistant to help with the process. LEUNG is not available for the tests, so LAI offers to be POK’s assistant on the experiment day. HANG and his team suppose they have arrested the prime suspect for the acid attack, but their guess turns out to be all wrong. POK manages to prove LEUNG’s innocence with his expert analysis……