Red Chinese agent Wo Fat uses a sensory deprivation chamber to procure information from U.S. agents. Steve McGarrett, head of Hawaii Five-O, investigates the death of a close friend who appears to have drowned. Steve's knowledge about his friend and a mysterious white substance lead him into a high-level intelligence matter involving a foreign agent. McGarrett, head of Hawaii's state police force, poses as "control," possessor of the names of other agents. He allows himself to be captured and placed in the chamber; will he be able to withstand the torture?

McGarrett is caught and cocooned, and must escape this torture and shut down Wo Fat's operation.

When the son of McGarrett's sister falls ill with cancer and she becomes involved in ‘naturology', her husband calls in Steve to investigate and persuade her to stop paying for the useless treatments. However, the quack doctor sets up a court case to prevent McGarrett from closing her practice.

McGarrett must use all legal means possible to win the court case against Dr. C.L. Fremont, stopping her fake treatments and saving his sister from more anguish and pain.

Two young men play an increasingly dangerous and deadly game for the attentions of a beautiful but spoiled heiress, who plays them off against each other.

Lew Morgan and his wife are friends of Danno, but she is murdered, and Morgan sets out to find the culprit. However, his wife seems to be hiding secrets that may have caused her death.