A peculiar disappearance case leaves Uncle Shan (Hui Siu Hung) mourning the loss of his beloved wife, Aunty Shan. It also results in Chong Yi Jing (Samantha Ko) growing up without a mother's love. Uncle Shan was a locksmith, running a shop called 'Integrity.' However, due to an unexpected incident, he developed dementia. He later takes on a devoted apprentice, Cheng Ho-Yan (Philip Keung). Ho-Yan inherits Uncle Shan's exceptional locksmithing skills, becoming a master at opening locks, even surpassing his mentor. Because of his remarkable abilities, he's frequently called upon by the police, and this leads to a friendship with Detective Lau Yip-Sun (Raymond Wong). To this day, there hasn't been a lock that Ho-Yan couldn't open.