McGarrett brings his mother back to the island. But her life may be in danger after Wo Fat escapes from prison with the help of an unlikely partner: Frank Delano.
Five-0 discovers a terrorist cell on the island; Danny has a flashback to one of the most eventful days of his time as a Newark police officer in 2001.
McGarrett is convinced that a psychiatrist murdered one of her patients, but will she get the last laugh? Meanwhile, Catherine discovers that an assassin is on the island and is looking for Doris McGarrett.
McGarrett discovers that a botched bank robbery actually wasn't about the money, while Danny protects a Victoria's Secret supermodel who has been threatened by a stalker.
McGarrett and a young girl are held hostage by a diamond thief during a campout, and Kono's boyfriend, Adam, welcomes his brother back from prison and gives him an offer to become a legitimate businessman.
A college professor is murdered, but who is the killer: his boss, his teaching assistant, or one of his students? Meanwhile, Kono is assigned to protect an annoying witness released from federal prison.
Chin Ho is drugged, kidnapped, and placed in a maximum security prison as retaliation for Frank Delano's death, but will he be able to make it out alive?
The governor asks Five-0 to handle a delicate investigation involving a dead prostitute, but is he really trying to cover up the case for an important political ally?
McGarrett and Danny's plans to go to the NFL Pro Bowl are interrupted when a computer executive is murdered during a team-building exercise at a corporate retreat.
Five-0 discovers that a murdered kindergarten teacher had a secret life as a roller derby star, and some very important information is stolen from Doris McGarrett's safe and could put her in danger.
After an explosion on a shark tour boat, one of the boat's owners is found dead in a submerged shark cage. Meanwhile, McGarrett helps Kamekona get his helicopter pilot license.
Five-0 discovers the body of a missing 17-year-old girl who was kidnapped 10 years earlier, and soon learn that the captors may already have a new victim. Meanwhile, Kono suspects that her boyfriend is keeping secrets from her.
McGarrett helps Doris on a dangerous mission to retrieve stolen microfiche, and Kono is shot while investigating a lead about Yakuza secret burial site that may be connected to her boyfriend.