Harry Potter and the Daughter of the Slytherin

The whole wizarding world seems to know what happened at Godric's Hollow in 1981. Lily and James Potter were killed, their son, however, somehow survived, causing the fall of Lord Voldemort - these are the facts and no one, not even Albus Dumbledore, has ever found any reason to question them. But what if the truth about that night is completely different? (AU following the GoF)