Chen Sing (Brother Chen) and Cheung Lik play two undercover agents who have been sent by their superiors to bust up a smuggling operation. Posing as prisoners they gain the confidence of a local jailed gangster played by Han Kuo Tsar. Together with Kuo Tsai they make their escape and vow to meet up later. When they finally reform Chen manages to infiltrate the gang, but some members suspect that he may be undercover. Kuo Tsai hears that Chen is under threat and defends him; but later, when it looks like Chen has no excuse for certain actions, he swears he'll kill Kou Tsai if he has been betrayed. Eventually brother Chen's cover is blown, he is overpowered, tied up and severely beaten. However he manages to surprise the guards, and that's when all hell breaks loose.