A mild-mannered school teacher is sent to prison after accidentally killing a man while protecting his younger sister. Inside Cell No. 4, he is forced to adapt to a harsh new reality alongside a group of eccentric inmates and a notorious troublemaker named Huỳnh Tấn Long. Despite the bleak environment and initial friction, Phúc's gentle nature gradually transforms the cell dynamic, leading the inmates to build an unlikely, tight-knit family that finds genuine joy, humor, and humanity behind bars.
