After a recent number of challenges, Billy Lo (Bruce Lee) and his friend Chin Ku (Huong Cheng Li) begin to suspect that someone wants them dead. Billy later visits his younger brother Bobby (Tong Lung), who is studying with Billy's former teacher, and leaves him a book on Jeet Kune Do. Chin is soon killed and Billy goes to Japan to find his stepdaughter, May. May tells him that Chin had visited just before his death, and left a film for her. They are suddenly attacked, but Billy manages to escape with the film.