A tsunami warning is called and a geneticist is evacuated from a conference. He is then kidnapped under the orders of Wo Fat, but he uses his diabetic medical condition as a ploy to stop Wo Fat from carrying out the plan to return him to China.

When a young son of a businessman escapes from captivity by ‘The Devil' and ‘Mr. Frog', Five-O must recover the $300,000 ransom money that the desperate father paid.

Two military policeman spot John Mala, a man who McGarrett has helped in the past, but who has gone AWOL. One of the policemen is shot, and tensions rise as Five-O and the army police clash in their techniques of investigation and their treatment of the local population.

Dr. Lemira, an opposition leader for Greece, is living in exile in Hawaii, but Klaus Marberg is sent to assassinate him. His plan is to get himself shot and work his way into Dr. Lemira's confidence so he can kill him easily. McGarrett must work out this plot and save the day before it is too late.

Five-O's efforts to rescue a young boy from kidnappers go wrong when Kono is captured and beaten. An angry McGarrett must work out a way to rescue Kono without further endangering him.

A Japanese computer research company executive is recognised by a veteran as his former captor in a Phillippine prison camp in World War II.

When a convicted murderer, Harry Kellem, hears a dying man say he committed the crime that Kellem was jailed for, he takes a doctor hostage and McGarrett must negotiate his way out of the situation.

A cowboy fears the loss of his land to a crooked estate agent and accidentally kills him by hitting him. McGarrett and his team must track the cowboy into the mountains and persuade him to give himself up.

Wo Fat and other top international agents converge on Hawaii to place bids on printing plates for twenty dollar bills, which are in the possession of a former friend of McGarrett.

Five-O must deal with treason, murder and double-crosses in order to solve the case and prevent the U.S. from being flooded by fake currency.

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.

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.

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.

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

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.

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.

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.

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

Army computer technician Jack Gulley kidnaps a scientist and then uses a planned heist by three accomplices on a military base to divert Five-O's attention from his sale of the scientist to the highest bidder.

Danno is found in the back of a truck, dazed and confused, and McGarrett and the others must help him piece together how he came to be in that situation.

Five-O has a suspect for a murder, but they have one problem. How can the suspect have been in two places at the same time?

A senior partner in a stock exchange firm comes up with a foolproof plan to rob the Honolulu Stock Exchange.

McGarrett and company must break through a tissue of lies in order to protect a Russian defector from being killed.

Chin Ho must face the fact that his daughter, Alia, is in love with the son of a local criminal under investigation, and that she plans to get married to him.

When a large amount of diseased rats are found on a boat with all the crew dead, Five-O must contend with an outbreak of bubonic plague.

Buildings are being set on fire on Sundays, and a known firebug is the top suspect. However, McGarrett begins to think that others may be responsible.

A corrupt federal agent who is tracking a man under indictment for tax evasion kills him for the $600,000 he is carrying, and then loses the money.

A string of five murders of wealthy men leads McGarrett to a crooked inheritance scheme.

A young man witnesses a murder, and finds himself and his family are now the killer's targets.

When a man is found dead with gold dust on him, McGarrett and his team must investigate where the stolen gold came from and how it is being bought onto the market.

A series of rapes and murders occur, and the main suspect seems to be a police officer...

When a letter bomb kills a Naval Officer whilst McGarrett is on Navy Duty, he is called upon to investigate and uncovers a plot involving an old nemesis...

McGarrett must try his utmost to foil Wo Fat's plans which include hostages and brainwashing.

A British agent, Harry Wells, arrives in Hawaii in pursuit of a turncoat, but not all is what it seems for Five-O...

A road accident starts the trail towards a plot to use SAM missiles to bring down a VIP jet plane.

A vice-principal enlists the help of his students and a submarine to smuggle drugs.

When Wo Fat steals toxins in an attempt to take out the leaders of Communist China, McGarrett must track him to Hong Kong.

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.