"We used to be friends, you know," Sirius blurted out, "best friends, even. Bellatrix and I were inseparable, and she taught me, laughed with me, gave me someone to trust."

What if Harry had a twin, and that twin was the boy-who-lived? What if when Voldemort's soul entered Harry, he was sent back to 1927? What if he made friends with a boy named Tom Marvolo Riddle?