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?
A psychiatric worker, George Loomis, is trying to drive a fellow Vietnam veteran Ted Frazer crazy in order to cover up the fact that he massacred his own platoon during an action. Loomis kidnaps boys and drugs Frazer to make it look like Frazer is mad and to blame for the tragedy. McGarrett and the team must unravel this web of lies and clear Frazer.
Chin Ho is accused of bribery, and cannot provide alibis for the nights in question. Worse, he is called to the middle of nowhere for a set-up. Chin's position is threatened, and the Governor orders an inquiry. McGarrett and the others must work out how Chin was framed and clear him of the accusations.
A doctor tracking venereal disease is murdered, and Five-O must track the series of encounters to find out who is a carrier. Their investigation is made doubly important by the murder of a young woman who is close to a upcoming politician. He seems a likely suspect but McGarrett suspects a deeper plot.
McGarrett must try his utmost to foil Wo Fat's plans which include hostages and brainwashing.
In Hong Kong, Steve is caught by Wo Fat and mentally and physically tortured by being 'reconditioned'. He must beat these problems to save the day again.
An Irish terrorist uses disguise and deception in order to be able to smuggle explosives for the Troubles.
When a sea-freighter is hijacked, the wealthy millionaire owner calls in Five-O, but all is not how it seems...
McGarrett must solve both a mysterious kidnapping and the problem of having a nosy reporter analysing his every move.
McGarrett engages in a personal struggle to clear the record of an officer and close friend accused of criminal activity.
Five-O must find out whether the death of an archaeologist is linked to his supposed desecration of tomb of King Kamehameha.
The return of a disgraced alcoholic policeman causes extra problems in the pursuit of a pair of armoured truck robbers.
McGarrett must deal with an astronaut turned real-estate salesman in order to crack the case of a murdered reporter.
When a Russian tennis star wants to defect, McGarrett must work to prevent an international incident.
A secret submarine, the murder of a Navy officer and strange amnesia create a puzzling case for Steve McGarrett.
A gang of university students plan a hoax tidal wave in order to steal priceless jewellery.
When an Asian ex-leader dies in a seemingly accidental swimming incident, his wife is convinced that he was murdered by forces from their home country.
McGarrett becomes involved in a love triangle between a young local man, a rich girl and her father who hates the Hawaiian origins of the boy.
A young doctor is suspected of having been involved in the murder of his mentor.
In order to find out the identity of the murderer of a union leader, McGarrett goes undercover as a longshoreman.
An up-and-coming young politician is blackmailed in order to affect his leadership of an congressional investigation.
While pursuing a drug dealer, McGarrett also has to contend with a federal agent.
Danno must deal with a surfer, one of his friends, who is suspected of the murder of a girl.
A female undercover cop threatens the progress of an investigation when she starts a relationship with a man connected to the case.
A Japanese businessman comes under attack from a young man whose father suffered in an Japanese Prisoner of War camp.
McGarrett must deal with an apparent mass murderer when a will creates a fortune for the last family member left alive.
A cryogenics institute comes under suspicion when an investigative writer becomes involved.
Five-O must deal with the kidnapping of an Arab princess, and Steve must also deal with an Italian female journalist's constant interruptions.
Five-O become involved in a complex case of body-switching, mystery investments and suitcases full of money.
Five-O's world is shattered when mobsters catch Chin Ho undercover and order him to be killed.
After a government agent is murdered, McGarrett must identify the traitor in a scientific facility.
When an astrologer visits McGarrett to inform him of a murderer with a terrible temper, his antagonism lessens when her assumptions seem to be partly true.
While McGarrett follows a false lead, an undercover Danno is discovered and brainwashed to carry out the assassination of Steve...
McGarrett is the lone hold-out in a trial where the guilt of the accused seems certain.
Steve is framed on the orders of a gambling syndicate, and becomes involved with a woman who is part of the case.
Five-O must deal with the plans of a Neo Nazi organisation to kill Bobby Tamara, the "Hawaiian Kennedy".
When a street robber claims that he stole King Tutankhamun's mask for fun, McGarrett suspects there is more to the case than simple robbery.
McGarrett assists a convict in his escape, so that he can go back to his gang and provide Five-O with inside information.
Danno is surprised when he bumps into a former flame and even more concerned when she seems to be involved in criminal activities.
The death of a prominent politician reveals a strange love triangle.
When a preacher is attacked by a man convinced that he is responsible for his wife's death, Five-O investigate more closely and discover some less than godly motives.
Two rival mobs attempt to take control of the disco scene in Honolulu.
The rival gangs are on the brink of all out war, and Five-O must struggle to stop them.
When a robbed bank vault shows no signs of break-in, an inside job seems the likely solution. McGarrett's trail of clues leads him back to the builder of the vault and his wife...
Millicent Shand returns and claims that her niece's husband has faked his own death in order to get his hands on $500,000.
A vacationing heiress seems unconcerned when McGarrett warns her that someone is after her ruby.
When a photographer takes a picture of a politician making a deal with an underworld figure, he tries blackmail. However, he is not prepared for the ruthless nature of the mobsters.
A private detective is rescuing girls from prostitution, and using the opportunity to kill the pimps as well.
When the son of one of Steve's friends dies of an overdose, he goes after a doctor that he suspects of over-prescribing drugs.
The hunt for a high-rise killer is made more difficult for Five-O when a journalist offers to share his profits in exchange for the killer's story.
When a woman dies due to heroin packets bursting inside her and the Governor is implicated, McGarrett and Danno head off to Singapore to discover a smuggling operation.
Five-O must close the heroin smuggling operation to exonerate the Governor and catch the figures behind the scheme.
Labouring under a ban on cooperation by native Hawaiians because of a Kahuna, McGarrett must try to prevent war on the streets...
The series concludes with the final showdown between McGarrett and Wo Fat. Three scientists have gone missing. They have one thing in common: they all attended a symposium that discussed a possible space-based, laser defense system. McGarrett impersonates a fourth scientist, Dr. Elton Raintree, who attended the same gathering and is soon abducted. Wo Fat is behind it all and wants the scientists to complete their work and produce such a device.
DVD extra
Behind-the-scenes documentary. (Originally aired on PBS in 1971).