Passing the Time with Demons

Set in Book 5 of HP: After the attack on the Potters on Halloween 1981, leaving James in the form of a crystal stag & Harry ditched at the Dursleys while leaving his twin brother to be hailed as BWL & raised by Lily, Harry and James, who finds a way to become human, finds themselves transported back in time to the Victorian era where they are saved- Rest of summary&warnings in chp1