Captain Grover is aided by McGarrett in his search for a friend who has disappeared, after it seems like he's committed murder. Kono persists in her quest to find Adam.

As a dangerous hurricane hits Oahu, Five-0 is tasked with protecting El Diablo, a captured serial killer who is being hunted by an assassin. Also, Tani's civilian safety check during the storm turns deadly and Rachel and Charlie evacuate to Danny's house, where the ex-spouses reminisce.