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The governor of Hawaii authorizes Navy intelligence officer Steve McGarrett to put together a special unit whose first job is to capture the man who killed McGarrett's father.
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The team works to rescue a computer expert who has been kidnapped by Serbian mobsters.
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When an escalating gang war spills into the stands of the local high school football game, injuring several bystanders and killing a gang leader, Five-0 uncovers an unlikely partnership between Samoan gangs and a mainland mob.
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McGarrett is on the trail of an escaped prisoner who is trying to take advantage of an opportunity to get his money back from his former crime partner.
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One daughter of the U.S. ambassador to the Philippines is killed and another daughter is missing, and governor Jameson brings McGarrett's team to lead the investigation.
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When the CEO of a hugely successful surf company is murdered, Kono revisits her past while Five-0 is thrown headlong into the varied but interconnected worlds of North Shore surfing.
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McGarrett places himself in the middle of a hostage situation on the USS Missouri. The hostage-taker is an ex-Navy SEAL suffering from post-traumatic stress disorder, who is the prime suspect in the murder of his wife.
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Danny's ex-partner from the Honolulu P.D., is found in a luau barbecue pit. Danny demands the team must take his word the man was incorruptible, although evidence piles up ha was involved in corruption surrounding the Mexican Ochoa cocaine cartel. Internal affairs Sergeant Cage, who wrecked Chin's reputation, is on the case but fails to shield it as HPD Detective Ahuna discretely joins the Five-O investigation. The deeper they dig, the dirtier everyone looks. Jailed drug dealer Sang Min holds a trump card, so Danny bids on it.
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Five-0 is assigned to help stop an assassination plot against a despicable foreign leader, with the help of one of McGarrett's old SEAL buddies. But is his friend actually in on the conspiracy?
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The team is on the trail of a team of bandits who are planning a robbery during the Honolulu triathlon, and they are forced to turn to Danno's ex-wife for help.
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After a woman escapes from abduction and her new husband is found dead in their hotel room, Five-0 discovers that they are dealing with a serial killer who targets newlywed couples.
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McGarrett discovers that the man who killed his father is still alive, and threatening to kill Chin Ho with a bomb unless his ransom demand is met.
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McGarrett's father's toolbox is stolen, and his sister is kidnapped for investigating their mother's death. McGarrett soon discovers that his father was investigating a suspected Yakuza leader before his death.
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Five-0 searches for identity and motive when a box with a severed head falls out of an overturned stolen car during a police chase–a task made more difficult when the driver dies at the scene.
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The island's leading tsunami expert is kidnapped on the same day that ocean reports indicate that a huge tsunami is headed to Hawaii. However, Five-0 soon suspects that the report is a hoax and is related to the kidnapping.
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McGarrett and Chin Ho try to rescue and protect a federal witness on the run from assassins, while Danny tries to get to the bottom of his daughter and ex-wife's carjacking.
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Five-0 searches for a group of Spring Breakers who are being held for ransom by a group of pirates.
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While Five-0 races to stop a mad bomber before he kills again, Danny gets an unexpected visit from his little brother, Matt, a fun-loving, Wall Street broker. The family reunion is cut short, however, when Danny discovers the real reason that Matt is in Hawaii.
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A costumed comics convention superhero fell to his death, pushed from his hotel balcony, but only as the victim of a drunk rooms mix-up. The team must work out how a ransacked room, no robbery, compromising pictures and adultery fit together. Steve rightly mistrusts a self-styled CIA-agent, works out she's a mere analyst and not even assigned, but decides to collaborate as she has indications his father's killer may have worked for Yakuza boss Wo Fat. Danny grumpily started dieting for his worried brat's sake.
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The team investigates the death of a commercial fisherman whose body was found in an unexpected place, while the imminent death of Chin Ho's aunt could reveal surprising new details about the stolen drug money.
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Five-0 turns up the heat on a crime boss after the safe house of an undercover police officer who infiltrated his organization is compromised and his wife is killed.
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While investigating the murder of a professional photographer, Five-0 discovers a connection to a local bookie. Meanwhile, Chin Ho covers for his uncle and claims that he has the stolen police money.
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Danny is exposed to sarin while Five-0 tries to track down Wo Fat, and Chin Ho's plan to quietly return the money his uncle stole hits a snag.
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After one of governor Jameson's assistants is killed, McGarrett discovers that the governor may have been working with Wo Fat and may have been the target of his father's investigation.