A peculiar disappearance case leaves Master Shan mourning the loss of his beloved wife. It also results in Zhang Yi Jing growing up without a mother's love. Master Shan was a locksmith, running a shop called 'Cheng Xin'. However, due to an unexpected incident, he developed dementia. He later takes on a devoted apprentice, Cheng Hao Ren. Hao Ren inherits Master 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 Officer Liu Ye Chen. To this day, there hasn't been a lock that Hao Ren couldn't open.However, during one locksmithing job, he reunites with an old friend, Lee Quan Kai, whom he hasn't seen in years. From that moment onwards, a series of strange events unfolds.