It's Christmas in Hawaii, but instead of celebrating, Five-0 is negotiating a hostage situation when the man who killed McGarrett's father resurfaces. The murderer, Victor Hesse, threatens to detonate an explosive that he's strapped to Chin Ho's chest.

McGarrett discovers new clues in his mother's murder when his sister is kidnapped.

When the sole witness in a high-profile murder case disappears, Five-0 must head into the jungle to locate and protect her from assassins who are closing in fast.

While hiking in a remote area of the jungle to see the famed petroglyphs, McGarrett and Danny instead find a homicide victim. Meanwhile, their aunt's failing health leads Kono and Chin Ho to visit home, where Kono finally learns the truth about the scandal that ended her cousin's career with the Honolulu Police Department.

Trapped inside a dilapidated building in Oahu’s Chinatown, Five-0 must protect a wounded Gabriel and plan their escape when enemy gunmen storm the building looking to kill him and anyone who gets in their way.

When an FBI agent who was cracking down on organized crime is killed, McGarrett rounds up every gang-related criminal on the island to find the culprit. Also, McGarrett tasks Adam with forming a new division within Five-0 to take on organized crime.

Five-0 struggles to stay a step ahead of a major tsunami that has the island evacuating its shores as they investigate the disappearance of the head of the Tsunami Warning Center.

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.

The attempted murder of a Pearl Harbor veteran leads Five-0 to use decades old evidence to investigate a deadly crime committed within the internment camps on Oahu during World War II.

A new ally helps McGarrett and Five-0 when mob bosses on the island are being targeted by an assassin. Also, Five-0 says goodbye to one of their own.

When Five-0 gets too close to the truth about Wo Fat and his associates, the criminal mastermind retaliates by trying to destroy the team. They've always played by their own rules, but when the Governor can no longer protect them, it's time for Five-0 to pay the consequences of their actions.

When a Navy SEAL, who's on the run for a murder he swears he didn't commit, takes hostages and safe haven aboard the U.S.S. Missouri memorial battleship, McGarrett must use every SEAL skill in his arsenal to diffuse the situation.

While McGarrett sits in prison awaiting trial for the murder of the governor, Danny brings him a surprise visitor to help clear him. Meanwhile, Kono is suspended from the force, pending an internal investigation.

Five-0 is in hot pursuit of a shooter who guns down one of their own, while another team member is forced to choose which of their kidnapped loved ones will live.

Five-0 must work with charming con man Hank Weber to find a killer when his female partner is murdered on the job. Also, San Francisco Police Inspector Abby Dunn comes to O’ahu and works with Chin to investigate the murders of five Chinese arms dealers.

A violent convict escapes from prison and kidnaps a young couple on vacation; McGarrett's estranged sister comes to town.

When a member of the security detail for an upcoming Aid Summit is murdered before he can reveal the details of an assassination plot, Five-0 is brought in to investigate the murder and protect the target, a ruthless dictator.

Five-0 is baffled when a highly skilled ring of thieves pulls off a heist of an armored car, killing two security guards but leaving the money behind. Their only lead in the case requires Danny to reluctantly ask his ex-wife for a favor.

When a crime lord moves against the family of an undercover NYPD detective who infiltrated his organization, it's up to Five-0 to stop the policeman from exacting revenge.

A grisly murder leads Five-0 to discover a ritualistic killing on Halloween, and the evidence suggests that the murderer will soon strike again.

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.

While the team investigates the murder of a young computer hacker, McGarrett tries to stage a long-needed reunion between his mother and his sister.

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.

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.

In an update of an episode from the original series, Five-0 tracks a killer targeting cops… and McGarrett is next on the list.