Police of Hong Kong have deviced a new day of fighting the crimes committed by the Canton authories to send three detectives into Hong Kong disguised as illegal immigrants. Their aim -- to infiltrate the biggest immigrant crime ring. The three get along better and better with police informer Da Da. They crack a few cases but their tendency to be violent makes Superintendent Cheng very uneasy. While the trio are looking for the core of the crime ring. The ring gets Da Da who is brutally murdered. One of the three is conned by a cabaret girl and he has his gory vengeance at Kai Tak airport. By accident, the ring approaches the trio to rob a bank. The police are tipped off...