McGarrett and Grover must work together to protect national security after they are tasked by the Governor to serve a warrant to a young computer hacker.

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

A neurosurgeon is assassinated just before performing a surgery. The investigation uncovers the truth behind the disappearance of four reform school boys over 40 years ago. Meanwhile, McGarrett's beloved Mercury Marquis is stolen by an unlikely culprit.

Five-0 enlists the help of a California ATF Agent to find a serial arsonist targeting couples on Oahu. Meanwhile, when Danny whisks Amber away for a romantic getaway, her abusive ex-husband tracks them down, intent on taking his wife back.

A case from 15 years ago forces Grover to take his family on the run when a dangerous mob boss tracks him down to seek revenge.

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