In a show with several similarities to the previous season opener, a series of swindlings are covers for serial murder. An Army sergeant who lost his brother in Vietnam because of the latter's infatuation with a bar girl, uses Honolulu bar girls as patsies to "marry" dead soldiers and collect on their $10,000 apiece insurance policies -- then murders them and keeps the money. The sergeant is absolutely coldblooded and utters the episode's title when his partner (who has been forging the marriage certificates and the insurance papers) has a heart attack and can't get ...
Nagata escapes from a mental institution, thinking it is December 1941. He had been part of a group called Black Dragons, a Japanese group that engaged in "fifth column" activities. Nagata upon escaping kills a guard, steals dynamite and constructs a time bomb. It turns out Nagata was supposed to blow up a fuel-storage facility at Pearl Harbor. McGarrett & Co. race to stop Nagata who also has his grown daughter, who he has mistaken for his wife, as a hostage.
Wo Fat returns. His men break into a center and send out a false tsunami warning. This provides cover so other of his operatives can kidnap a scientist. However, it turns out the scientist is a diabetic who requires insulin shots. This complicates Wo Fat's plans to remove the scientist from Hawaii. Five-O races to prevent Wo Fat from succeeding.
A businessman at a convention in Honolulu decides to indulge himself just a little bit more and plans a one-night stand with a prostitute. When he gets to her apartment, he hears a knock on the door and is told to hide on the terrace. The woman's new guest is a brutal mobster who throws her off the balcony to her death. The businessman has a Hobson's choice of reporting the crime and facing repercussions from his Kiwanish-like home town, not reporting it and having a guilty conscience, or what actually happens -- he doesn't report it, but the mobster's goons figure ...
A group of revolutionaries from a Latin American country have entered Hawaii illegally, raided an armory and stolen weapons and ammunition. Their leader is wounded and captured by McGarrett but his men manage to whisk him away from the hospital where he is being held. However, the leader, who has lost a lot of blood, will die without further medical attention. Five-O attempts to recapture the leader and stop the weapons from leaving Hawaii.
A federal agent is murdered on a plane bound for Hawaii. The investigation of this crime leads McGarrett and Five-O to uncover a terrorist plot by Dr. Erich Stoss to distribute a fungus that will wipe out the Hawaiian sugar cane crop, thereby destroying an industry and thereby forcing the U.S. and other countries to buy sugar from non-U.S. sources.
A group of college students devise a plan to break into Bishop Museum and steal King Kamehameha's cloak. A collection is started up and amnesty will be given if the cloak is returned. Meanwhile Five-o investigates and concludes that the college students stole the cloak. Kono tries to reason with one of the students, who is Hawaiian, and make him understand how wrong it was to steal the cloak. The others decide to keep the cloak rather than collect the reward. The Hawaiian student [Johnny) comes to Five-O headquarters and tells McGarrett that the others are planning to...
McGarrett receives a phone call from a woman in Singapore saying that she can witness against a local mobster. McGarret immediately flies to Singapore to retrieve her. The mobster in Hawaii knowing that the girl can finger him, has a contract put out on both McGarrett and the girl. Unable to get to the airport, they board a ship bound for the Philippines, where their lives are threatened again. As Chin Ho arrives in Manila, another hit man is waiting for them.
A state investigation centers on Mike Finney, a former racketeer who hasn't violated the law since moving to Hawaii nine years earlier. But Charles Irwin, an ambitious counsel for a state legislative committee, sees the probe as a way to further his political ambitions. For Five-O, the case begins when there is an apparent attempt on Irwin's life. McGarrett, who knows Finney, is also a target of Irwin. Meanwhile, the "syndicate" on the mainland, nervous that Finney is being investigated, sends a hitman to Hawaii to kill Finney.
Just as the ransom money has been delivered, the kidnap victim escapes; one of his two kidnappers falls to his death trying to chase him. The surviving kidnapper concocts another scheme: he holds the ransom money (which is hot) hostage and tries to coax the kidnapped boy's greedy father into laundering it for him. The kidnapper, an accomplished scuba diver (the source of the episode's title) plans to swim underwater to and from the dropoff point. Five-O identifies the kidnapper and tails him, at one point donning frog masks in an attempt to rub his nose in his ...
Jo Louise, a rich and spoiled heiress, is recklessly pitting two suitors, Craig and Billy, against each other. She's devised a game where each boyfriend draws a card and gets points for various stunts. This game has resulted in, among other things, an Army Jeep being burned and a boat sunk. Billy takes the lead by kidnapping a homeless person. Craig then demands the Joker -- 500 points for a kill. He intends to murder the homeless man. Five-O aims to put an end to the game before things reach a tragic end.
Ossie Connors, a brilliant and ruthless bank robber, devises a complicated scheme to get revenge on McGarrett, who put the criminal away 10 years earlier in what the lawman describes as "my first big arrest." Connors bribes a Five-O snitch to mislead Dan Williams, then has the snitch killed. Before the tale ends, three more people will lose their lives. McGarrett, relying on cop's instinct, resists what appears to be an easy end to the case.
McGarrett survives a bombing of his car but is blinded. His sight may or may not return. He begins rehabilitation under the no-nonsense supervision of Nurse Lavallo. Five-O's investigation fails to turn up a suspect among known criminals. Meanwhile, McGarrett's attacker is determined the kill the lawman in the hospital where he is undergoing rehabilitation.
The "lost" episode of Five-O, it has never been made available in syndication. A woman is found hanged to death. The suspect is a young man who uses a yoga technique where someone hangs themselves (but survives). All is not what it appears.
Ted Frazer, a Vietnam veteran, thinks he is cracking from mental strain. In reality, he is being tormented by fellow vet George Loomis. George makes Ted think he is kidnapping children (who George has really abducted). Ted's mother also wants nothing to do with him, increasing his emotional strain. McGarrett & Co. determine there's something wrong with George's story; he has told Five-O he was in Vietnam at about the same time as Ted when, in fact, they served in the same unit. Five-O must determine the motives behind George's lies. The answer lies in an incident that...
Honolulu policeman Lew Morgan appears to be cracking after his wife is killed. Morgan also is an old friend of Five-O's Dan Williams, who takes a personal interest in the case. It turns out that Morgan's wife, Marjorie, had affairs with other men. The lead suspect is Gary Oliver, a criminal who was Mrs. Morgan's latest lover. Morgan kills Oliver, an apparent case of a grief-stricken husband taking vengeance. But Five-O's probe shows the case is more complicated.
Dr. Royce, a scientist with an expertise that can be used in the underwater detection of ships, is lured by enemy agents and his girlfriend to defect to a foreign power. McGarrett is both helped and hindered by a federal agent named Merrill Carson in trying to prevent Royce from leaving the island with the enemy agents, even as Dr. Royce gradually realizes that he is more a prisoner than a willing defector.
Alexander Kline, a brilliant scientist who had worked for the U.S. government, creates the Q strain, a bacteria that can wipe out vast numbers of people in a short time. He quit his U.S. position. To protest research into biological weapons, he will use the Q strain to wipe out Hawaii's population. Five-O catches up to Kline but the scientist has already left a vial with the killer bacteria in a place where it will spread.
Alexander Kline, even under intense questioning, refuses to reveal the location of the vial containing the Q strain. McGarrett gambles that by letting him go, Kline can be convinced to change his mind. Kline has fallen in love with a woman, who convinces him to not follow through with his plan. But, even as he relents, the vial with the killer bacteria is not at the dock where he placed it.
A jeweler in New York City is murdered after making a paste copy of the "Queen of Polynesia", a valuable and historic emerald about to be donated to the State of Hawaii. The 5-0 squad suspects that a switch might be planned at the unveiling ceremony. Jewel thief Janet Kingston, under the pseudonym Camilla Carver, and her sidekick Michael develop a scheme to get into the unveiling when Michael observes one of the invited guests, former Broadway star Thurman Elliott, stealing a diamond bracelet at a society party. Carver and Michael blackmail Elliott into taking her to ...