Hong Kong Customs and Excise Department officers Chow Ching-lai and Cheung Wan-nam share a close mentor-student relationship. On a case involving seized smuggled arms, Ching-lai is sent to take part in a joint operation with Interpol to capture a reclusive arms dealer. However, Wan-nam makes a drastic decision that further complicates the case.

Two lonely souls meet in a bar on an ordinary night. United by a familiar-looking lighter and a familiar tune, they seem to have known each other long ago. Tung is a singer-songwriter who barely makes his living while Niki is just out of a relationship. They meet in a bar and a feeling of déjà vu hits them. Later into the night, they bump into each other again at the laundry store. The lighter and melody light up the chemistry between them. Two strangers open their hearts and share their magical, intimate feelings for each other as smoke slowly rises upwards.