An army sergeant and a office worker have a scam in which they use bar girls to claim G.I. widow benefits, and then murder them to take the cash. McGarrett and company must use the girls to get to the core of the plot.

A Japanese World War II veteran, Yoshio Nagata, escapes from a mental hospital and tries to carry out his wartime orders to blow up a refinery.

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.

A middle-aged mainland hardware salesman uses a prostitute, and then witnesses her murder by a mobster. He refuses to testify because of the damage to his reputation and that he doesn't want to be involved. McGarrett must persuade him to do the right thing.

A university professor, Dr. Paul Farrar, is using hypnosis to programme students into becoming assassins. McGarrett uses a policewoman as bait for Dr. Farrar, but the plan goes wrong and her life is put in danger.

McGarrett must counter a threat by international terrorist Erich Stoss to use a fungus to wipe out Hawaii's sugar cane, half of the world's supply.

Four university students hatch a plot to steal the robes of King Kamehameha, and McGarrett and the team must apply pressure to the gang's weak point to retrieve the robes and catch the thieves.

McGarrett gets a phone call from Singapore and goes to rescue Nicole Wylie, a witness who has changed her mind and wants to testify. However, the pair must face many dangers on their return trip back to Hawaii.

An assassination attempt on a prominent politician, Charles Irwin, leads Five-O to Mike Finney, a former racketeer who has been clean for nine years. However, Finney insists he is innocent, and the trail of clues leads right back to Irwin.

When a dictator's plane is diverted to Hawaii as part of a plan to kill him, McGarrett must deal with the complex politics of the situation and protect the hated leader.

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 young men play an increasingly dangerous and deadly game for the attentions of a beautiful but spoiled heiress, who plays them off against each other.

A career criminal, Connors, fools McGarrett and the team into protecting the wrong bank, and robs a nearby one, taking the wife of the manager hostage. Things turn ugly when one of his goons assaults and murders her. McGarrett must race to capture Connors before he can do any more damage.

McGarrett gets a surprise birthday party, but when he goes to pack the presents in his car, it explodes and blinds him. Danno, Chin Ho and Kono must work to catch those responsible, whilst McGarrett has to get used to not having his eyesight.

Don Miles, a health freak, uses a hanging-type exercise to promote his wellbeing, but his girlfriend Wanda tries it, and seemingly dies in the attempt. However, all is not what it seems…

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.

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.

Peter Corman is murdered during a game of poker, and his brother Lorenzo arrives in Hawaii for revenge. McGarrett must work out what happened and prevent Lorenzo from carrying out his intentions.

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.

Lew Morgan and his wife are friends of Danno, but she is murdered, and Morgan sets out to find the culprit. However, his wife seems to be hiding secrets that may have caused her death.

A research scientist, Dr. Royce, is set up by revolutionaries to be transported away from the islands in a submarine. McGarrett must stop this from happening and also has to contend with the interference of federal agents in the case.

Dr. Alexander Kline, a biological scientist, views his work as evil, and to prove it, he plans to unleash a deadly germ that would kill thousands. Three dead cows lead McGarrett on a desperate chase to track down the toxin, involving a friendly telephone operator and top Washington agents.

Dr. Kline's deadly toxin is lost, he is having second thoughts about his plan, and McGarrett has to find the vial before it disintegrates and poisons the whole island. Already the toxin is doing its deadly work as innocent people come into contact with it.

Camilla Carver, a con-artist, blackmails a politician to take her to an event where she can steal the priceless Queen of Polynesia emerald and swap it for a fake. However, McGarrett and the team are at the event and make sure that neither the gem, Carver or her accomplice vanish.