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.

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 jewelry.

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.