The new Chemistry teacher Lam Yau discovers that his colleagues avoid discussing his predecessor Ng Yu. Out of curiosity, he starts to collect evidence and attempts to find out the truth. He suspects a student of murdering Ng, so he confronts him face to face...林悠是剛上任的化學老師，聽到該校老師談及吳宇（前任化學老師）時欲言又止，感到奇怪。在好奇心驅使下，他努力查明真相。林悠不斷搜集證據，後來發現學生何清形跡可疑，懷疑何清殺死吳宇。為了證實事情的真相，林悠與何清在一處無人的地方對峙......
