After losing both parents at a young age, Lai Yat-tsau becomes a parent figure for his three younger sisters. His mother’s death and his father’s fall to drug addiction turned Yat-tsau into a very quick-tempered and chauvinistic man. Originally assigned to the Kwun Tong Police Station, Yat-tsau’s superior transfers him to the K-9 unit to work with police dogs, hoping that the strict training would better shape his character. At this new department, he develops a partnership with veterinarian Ma Chi-ho, who helps him solve cases for the police.