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 organization 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.
