Five-0 combs a convention to find the killer of a sci-fi fan who was thrown out of a high-rise window. A CIA agent who's interested in the Yakuza that killed McGarrett's parents shows up in town to meet with Steve.

With the invaluable information that was shared by Agent Jenna Kaye, Five-0 is closer than ever to capturing Wo Fat. Their mission takes an abrupt turn, however, when Danny is exposed to a lethal neurological agent that presents an even greater threat: bio-terrorism on the island.

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.

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.

Gov. Denning assigns Officer Lori Weston to Five-0 to make sure McGarrett and team follow the new rules set by him and also apply her excellent profiling skills to the task force. Meanwhile, as Five-0 investigates the kidnapping of a teenage paddleboard champion, Internal Affairs Capt. Vince Fryer continues his interrogation of Kono.

McGarrett finds himself in need of the Five-0’s help when he goes to North Korea with Jenna Kaye to deliver a ransom to rebels who are holding her fiancé hostage. Meanwhile, the Five-0 investigate the murder of an investigative reporter who seems to have ties to Jenna.

When McGarrett is kidnapped by Wo Fat, he experiences what would have happened to the team if they had taken a very different path, on the 100th episode.