Maw, a Myanmar engineer, has been promoted to Deputy Head of Production, bringing along his younger sister Sin to work in the same factory under the supervision of Nui, the Quality Control Manager. The promotion and Sin's arrival create suspicion among some factory employees, including Wit, Head of Production Line A, who has been at odds with Maw throughout their working relationship. A tense atmosphere blankets the entire factory, intensifying several times over on the first night of these changes, leading to a mysterious murder case that claims the life of Saw, Maw's close friend, who disappears into the shadows. To uncover the truth, Inspector Narong leads his team to work the case, investigating to find out... who is the killer?