Lee (Bruce Lee), a student at the Shaolin Temple, is approached by British intelligence to infiltrate a martial arts tournament held on Han’s Island.  Mr. Han is suspected of using the contest as a cover for drug trafficking and prostitution rackets. It is Lee’s mission to gather evidence but he also has his own personal reasons for agreeing to the mission when he discovers the truth behind his sister’s death.

Other attending Han’s tournament include Roper (John Saxon), a gambling addict that uses it as a way to escape some of the debts and the people coming to collect.  Williams (Jim Kelly) also flees to the Island after he is harassed by racist police officers.

Once they arrive on the island, the fighters are greeted with a lavish feast where they get a taste of Mr. Han’s hospitality. Lee does not waste any time and soon makes contact with an undercover operative, Mei Ling, and sneaks into Han’s compound later that night to look for evidence. He is discovered by the guards but manages to make an escape.

The next morning, Han orders the execution of the guards who failed to him. He had given the fighters strict instructions not to leave the rooms at night and later confronts Williams as being the suspected intruder.

Determined to find the evidence he needs, Lee sneaks out again the following night but this time is captured after battling with the guards. Roper is forced to fight Lee but when he refuses, Han commands that his men to kill them both. When the fight doesn’t quite go to plan, Han escapes into his hidden room of mirrors for a final confrontation.