 An ex-cop who s a recovering alcoholic returns to Hawaii after a long stint on the mainland in order to make amends to McGarrett (the "ninth step" of Alcoholics Anonymous) -- he was drunk on duty and failed to stop an armored-car heist which led to the theft of a fortune and the death of the car s driver. But McGarrett discovers that the cop s drink was drugged in advance by the thieves and their accomplice (the ex-cop s ex-girlfriend) -- and they are planning still another heist to replace the money, lost in a car explosion at the beginning of the show. When the disgraced cop launches an investigation of his own, he puts his life in grave danger.