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.
A hard-as-nails Texas Ranger arrives on the island to look for his missing daughter, Kono and Adam's secure location is compromised, and an old friend comes to Catherine with a job offer.
A married couple's execution leads Five-0 to a mystery involving stolen artifacts and a long-forgotten secret society, and Catherine goes through her last day with the Navy.
McGarrett tries to find the man who killed his old SEAL friend Billy while he and Catherine were working a surveillance job, and he also turns to Joe White to track down his mother.
Five-0 tries to figure out who killed an officer who was working undercover for the ATF, while also babysitting for McGarrett's sister Mary's new baby.
A Secret-Servince agent's death leads Five-0 to believe that an assassin is targeting the President during his trip to Hawaii; McGarrett gets a surprise Thanksgiving visit from his Aunt Deb.
A murder attempt on a Pearl Harbor veteran leads Five-0 to use decades old evidence to investigate a deadly crime committed in an internment camp on Oahu during WWII.