When a crime lord moves against the family of an undercover NYPD detective who infiltrated his organization, it's up to Five-0 to stop the policeman from exacting revenge.

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.