The third season of Hawaii Five-0 picks up where season two left off, with Chin Ho being forced to choose between saving his wife or his cousin. McGarrett escorts his mother back to Hawaii and realizes she is in danger but question whether his mother may be keeping from him. Meanwhile, the team turns to ex-con and art expert August March to help hunt down a group of thieves.
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.
When Danny is forced to remain completely still while bomb technicians disarm a bomb that he has accidentally almost triggered, McGarrett distracts him by getting his partner to tell the story about his toughest and most emotional case from his days as a cop in New Jersey.
McGarrett plays cat and mouse with a smart and seductive therapist he believes murdered her patient. Meanwhile, Catherine must hunt down one of Doris's old targets who is now seeking revenge.
Max and his crush (Rumer Willis) get put in harm’s way when a botched bank robbery leads the team to determine that the criminals had very unexpected motives. Meanwhile, Danny is stuck with the tough task of coming to the rescue of the most beautiful women in the world when a stalker goes after a Victoria’s Secret model.
An Aloha Girls camping trip with Grace turns deadly when an armed man takes McGarrett and a little girl hostage. Meanwhile, Adam introduces Kono to his dangerous brother who was recently released from prison.
Danny and McGarrett investigate the murder of an Oahu University professor whose body is found decomposing in a tub of acid and his boss, his teaching assistant and a student who he busted for cheating are all viable suspects.
Chin Ho is kidnapped and wakes to find himself trapped in Halawa prison disguised as an inmate. With no time to waste, the team must bypass the rules to save Chon Ho’s life.
The team is directed to investigate when a prostitute is murdered in a Congressman's home, who is nowhere to be found. Danny has his own drama as the custody hearing regarding Grace goes to court.
As the island prepares itself for the Pro Bowl, an executive from a California technology company is found dead after a tactical ops team building exercise. Unexpectedly, a star running back from the football game (Arian Foster) winds up helping Five-0 during the investigation.
While apprehending his latest fugitive, Dog the Bounty Hunter is witness to a woman falling off a balcony to her death. Five-0's trail leads them to discover that the victim lead a double life as a roller derby player. Unable to get any useful information about the victim from her teammates, Catherine is asked to go undercover as the team's jammer. Doris comes home to find a burglar robbing her stash of sensitive information.
When threats turn deadly against a tour company that endangers the local shark population, Five-0 faces the difficult task of narrowing down the suspect list. Meanwhile, the team debates whether or not Kamekona will earn his helicopter license.
McGarrett and Catherine head into North Korea to retrieve a fallen friend's body. While there, McGarrett recalls his last perilous mission in the country.
When the body of a young girl who was kidnapped 10 years earlier is discovered, Five-0 must hunt down the kidnappers who have now taken their next victim. Meanwhile, Kono asks Catherine for a favor that could damage her relationship with Adam.
McGarrett must help his mother execute a covert op to retrieve an incriminating microfiche. Meanwhile, Kono’s life is in danger when she closes in on Adam’s secret.
When a plane lands on Oahu with four bodies on board and a missing terrorist detainee, the CIA tasks Five-0 with finding him before he carries out an attack on U.S. soil. Meanwhile, Kono is on the run from the police for a murder she did not commit, and McGarrett’s prison visit to Wo Fat ends with a shocking discovery.