Former SWAT captain Lou Grover of HPD, has a love and hate relationship with McGarrett who pointed a gun at him and his SWAT team to free three prisoners in order to rescue Catherine in the season 4 premiere. He is later forced to work with McGarrett on an assignment ordered by Governor Denning to serve a warrant for a computer hacker, where he and McGarrett become friends. He has a daughter who moved from Chicago to Hawaii with him to start a new life.His past is revealed in "Pale 'la" ("Buried Secrets") where he failed to save a boy who was taken hostage by his father, who Grover knew. It resulted in both father and his son's death.In the season finale of season 4, Grover's action to rescue his daughter is force to retire by HPD but Steve offer him a part of 5-0 which he accepts.