Chan, an articulate senior detective nearing the end of his career, is taking care of the daughter of a witness killed by ruthless crime lord Po. Martial arts expert Ma is set to take over as head of the crime unit, replacing Chan who wants an early retirement.

In 1992, a heavy rainstorm caused massive power outage in Hong Kong. At that night, two young astrology enthusiasts, Moon and Sun, met under the starry night by the seaside. When their affection to each other grew, Sun was admitted into a boarding school and would move to another country in a few months under his father’s plan. Like the sun and moon, the couple could hardly see each other despite that they were living in the same city, but their love endured amidst the separation and opposition from Moon’s mother. Overcoming the challenges from teachers, friends and family, time has come for Sun to depart…