When the Five-0 discover a John Doe in the trunk of a stolen car, they not only have to find a killer, but also need to figure out who the physically-altered victim was. Meanwhile, a homeless Danno is sleeping on McGarrett’s couch.

Five-0 crosses paths with Tony Archer, a retired NYPD bomb expert who is now a private investigator on Oahu, when they investigate the death of famous talk radio DJ Bobby Raines.

Five-0 and the NCIS: Los Angeles task force team up in Hawaii when there’s a suspect on the loose who is threatening to release a deadly virus into the population.

The crossover continues on NCIS: Los Angeles S03E21 Touch of Death (II).

The team goes after Wo Fat and Delano for the death of an important person. Steve must resolve the issues between him and his "dead" mother, once he finds her alive and well.

An investigation involving a potential serial killer puts Chin's life in danger; Grace and Danny find a mysterious puzzle box.

A man is shot as his daughter is abducted; Danny tries to reunite his parents; Jerry finds a code on McGarrett's champ box.

When Grover's daughter is kidnapped by an old nemesis, he is forced to help steal $100 million in order to get her back. Meanwhile, Wo Fat escapes prison and heads back to Oahu.

The island of O’ahu goes on lockdown when Five-0 hunts a terrorist who starts using weaponized drones on civilians. Meanwhile, McGarrett and Danno must go for a mandated review with a psychologist, resulting in a session which looks a lot like couples therapy.

On the fourth anniversary of his father's death, McGarrett meets a woman who helps him reopen the last unsolved case his dad worked on before he died.

On the eve of Kono’s wedding to Adam, Five-0 must stop a fanatical patriot intent on starting a new war on terror by detonating stolen nuclear warheads and framing a terrorist leader.

A murder leads Five-0 to investigate a centuries-old Oahu palace raid involving pirates, buried treasure and a killer who is using a stolen painting as a map. Also, the morning after their wedding, Kono and Adam are threatened and tortured by Gabriel, and Danny shows concern for McGarrett regarding Catherine's return to the island.

When the bodies of two serial killers are found on Five-0 property with chess pieces in their mouths, McGarrett and the team hunt for a vigilante as fear grows that tourists aren't safe in Hawaii.

While working the murder case of one of the last survivors of the USS Arizona, McGarrett learns about his grandfather's important role at Pearl Harbor. Also, Adam uncovers bone fragments at his new construction job and asks Jerry to help him discreetly investigate.

McGarrett risks his life when Five-0 attempts their most dangerous rescue yet of young girls trapped in the sex trafficking ring they have been tracking this year. Also, Kono, deeply affected by the case, makes a life-changing decision.

McGarrett and Danny recruit Tani Rey to join the task force when diabolical hacker Aaron Wright releases a dangerous arsonist from prison.

Junior and Adam back up McGarrett when a bank heist in progress forces Steve to make a potentially heartbreaking mistake. Also, Adam is forced to face an empty home without Kono

McGarrett and Danny investigate the murder of a private detective whose client was killed the same way, and Adam sends Jessie into a dangerous situation with disastrous consequences. Also, Danny’s uncle, Vito, comes to town to help Danny and McGarrett get their restaurant up and running.

Catherine Rollins recruits McGarrett and Jerry to help her track down a uranium deposit thought to be hidden on an abandoned Hawaiian island before a suspected terrorist can make dirty bombs with it. Also, when Junior falls and is trapped in a ravine, he reflects on his estranged relationship with his father.

McGarrett and Five-0 discover a Russian spy ring hiding in plain site on Oahu when a Russian nuclear attack submarine appears on the coast of Waikiki. Also, Tani is conflicted by her unnerving discovery at Adam's house.

After Steve’s CIA agent friend is killed, McGarrett lets himself be captured by the group he thinks is responsible and endures a torturous sensory deprivation tank to find the killer. Also, Tani wrestles with whether or not she will tell McGarrett about the murder weapon she found at Adam’s house.

McGarrett investigates a cold case from the 1940s, one that his grandfather and the famous Honolulu detective Chang Apana worked on, and he tries to deduce how the case could have been solved. Also, McGarrett and Danny get ready for the opening of their restaurant.