When the explosive expert Wong plans to deliver his new invention, a small bomb to someone, his assistant Lung is aware of the plot. But when Lung steals the bomb and wants to present it to the police, he killed by Wong and another two killers. A taxi driver, Chu, along with a chemist, Lam and a girl, Cat witness the murder scene, getting involved in it. Just prior to Lung death, he cleverly hides the bomb at a secret place and reveals the clues only to Cat. Being afraid that the three people might find out the bomb and ruin his plot, Wong appoints some killers to get rid of them. After going through a great deal of difficulties, the three people find out the bomb but Wong also knows their location. At the end, a piece of evidence is singled out and safely delivered to the police and all the villains are rounded up. (Joy Sales)