Desmond wakes up and realizes he is back on the island.
Five-0 enlists the help of a California ATF Agent to find a serial arsonist targeting couples on Oahu. Meanwhile, when Danny whisks Amber away for a romantic getaway, her abusive ex-husband tracks them down, intent on taking his wife back.
When a local girl’s death is ruled a suicide, Abby challenges her father, the Sheriff, to investigate what really happened. As the wedding approaches, Trish must come to a decision about Hunter.
