Super-intelligent but shy math teacher Shi Hong (Zhang Lu Yi) falls in love with his neighbor – a single mother named Chen Jing (Ruby Lin). His neighbor, who lives with her young daughter, is not aware that Shi Hong often listens in to her domestic conversations through the thin walls that divide their homes. Things take a sudden turn for the worse when Chen Jing's former husband arrives on the scene, demanding money from her, and threatening to harm her and her daughter if he does not get what he is after. A scuffle ensues, and her ex-husband is killed. Shi Hong – a witness to everything – turns up and attempts to help Chen Jing and her daughter dispose of the evidence linking her to the crime. But he has not counted on his old school friend and fellow child math prodigy Tang Chuan (Wang Kai) being the detective assigned to the case. Will Tang Chuan discover the truth behind the death of Chen Jing’s ex-husband? Or will Shi Hong outwit his former classmate? The movie was based on a novel of the same name, written by mystery novel author Keigo Higashino. The novel was the third in the author’s popular “Detective Galileo” series. “The Devotion of Suspect X” is a 2017 Chinese film directed by Alec Su.