McGarrett is floating in a sensory-deprivation tank. He's brought out and comes face to face with Wo Fat. But it was a hallucination. Flashback to two days earlier. McGarrett and Junior are digging a pit in which to bury Kamekona's money for the restaurant. McGarrett gets a call that upsets him. Hennessey, a CIA agent who had helped him, has been killed. A burglar is tossing Hennessey's apartment and burning notes he found. McGarrett and Danny arrive. He attacks them, but they eventually prevail. Two other CIA agents come to the apartment, including Greer, who McGarrett once dated. Tani hasn't told McGarrett about the gun she found at Adam's house. She's afraid to get it tested. Greer tells McGarrett that five agents had died in accidents in recent months. She suspects there's a mole in the CIA. The burned pieces from Hennessey's apartment yield the name of a ship. McGarrett sneaks on board as a construction worker. He discovers a sensory-deprivation tank. McGarrett and the CIA leader, Kray, come up with a plan in which McGarrett allows himself to get caught and feeds them bad intel. Everyone is afraid he's going to get brainwashed. McGarrett gets drugged. Before he passes out, he sees the mole, Greer. McGarrett gets stuck into the tank, while everyone waits impatiently outside. He feeds them the false information. Greer sees movement and calls out backup. Jerry shoots off a flare, and a gun battle ensues. Junior drops a crane on top of the ship, which allows Tani to sneak onboard unseen. Jerry mows down shooters with his SUV. McGarrett battles the forces inside, including their leader, Kang, who Danny shoots dead. Greer takes the false information back to her conspirators.