Reggie Cole, an undercover NYPD officer is in Hawaii and squeezes in a brief visit with his family before returning undercover to run security for his mobster boss, Cannon. Unfortunately, on their one night together, they are attacked. Though his son is unharmed, Reggie's injured and his wife is murdered. McGarrett and his team investigate the shooting and Cannon is their prime suspect. Cannon has come to Hawaii to visit his son who isn't in the family "business"; he claims not to have known Reggie was undercover but he remains a prime suspect. Meanwhile, Reggie decides to leave the hospital and do his investigation, but when 5-0 discovers the dead body of one of the shooters, they are forced to track down Reggie in case he's avenging the deaths of his wife. They find Reggie and learn that someone else is killing the killers. Using evidence Reggie found, they bring down the final shooter and get him to confess who hired him. Turns out it wasn't Cannon, but his son. Even though Cannon's son wasn't a mobster, he enjoyed a lifestyle supported by his father's crimes and when he heard the FBI was going to bring in his father, he went after the person who threatened his inheritance.