A psychotic man named Ralston is killing the wives of members of his army unit, and Five-O, including Kono on his last case, must stop him before he commits any more crazed attacks.

Danno goes undercover onboard a Navy ship to try and uncover how sailors are smuggling heroin onto the islands.

A young widow becomes part of a blackmail plot involving the murder of a Chicago mobster.

McGarrett sets up a cordon of police around a young woman to capture her boyfriend who has escaped from jail, but all is not as it seems…

Three real estate crooks die horrible and mysterious shellfish related deaths, and McGarrett and the others must establish the link between them, and who has reason to want them dead.

An eccentric billionaire is accused of murdering a business associate, but will not leave his boat to defend himself against the accusations, allowing his associates to declare him mentally incompetent.

When a young woman is beaten and raped and a soldier is arrested for the crime, McGarrett begins to have doubts about his guilt.

Several faces from the past reappear as McGarrett must stop Wo Fat from carrying out his plan, a ninety second attack on a missile tracking base.

McGarrett is framed in an elaborate set up by Wo Fat, and has to contend with a foreign double amongst other problems.

A woman attempts suicide in order to get her boyfriend to come out into the open and expose himself to an assassination attempt.

A veteran criminal who has already had dealings with Five-O escapes, and plans to steal millions of dollars from drug smugglers.

McGarrett and the team must find out who is behind a series of ecological stunts, when it is feared that a company executive will be their next target.

A mob boss seeks revenge on a former boxer who smashed the hand of a novice to prevent him from ending up ruining his life in the boxing ring.

McGarrett must deal with the conflicts between four gangs of differing ethnic background, and try to uncover illegal activities.

A policeman who was kicked off the force blames McGarrett and Five-O and plans to kill the Governor.

McGarrett finds holes in a convict's story and a husband becomes a suspect in the murder of his wife.

Five seemingly good citizens with different motives band together to steal $6,000,000 while McGarrett is away on Maui at a trial.

While investigating the death of a security agent at an airport, McGarrett comes into contact with a gang who hijack cargo.

Young Vietnam veteran and marksman Billy Shem Jr. buys a rifle under false pretences and proceeds to a bunker at Diamond Head. He then takes pot shots at the people on the road and then the police who arrive. McGarrett must neutralise the threat he poses by any means possible.

A hippie robs an embezzler of the key to a locker containing $250,000. Meanwhile, Danno is trying to contact the daughter of his Berkeley University landlady, who happens to be the hippie's girlfriend…

Five-O is up against a sophisticated gang who have come to Hawaii to cash $750,000 of traveller's cheques.

Vic Tanaka is murdering women and painting their faces to resemble a prostitute he once knew, who is now happily married. McGarrett and his team must find the killer before he does any more damage.

Gangster Johnny Oporta arranges for his enemies to be murdered and then covers up his crimes by incinerating their bodies. McGarrett and the others must stop this murderous spree.

A ten year old case is reopened when an archaeological dig unearths the skeletons of two murder victims.