The Muggle

When Lily and James were marked for death, Lily swore to do everything in her power to keep Harry safe. 16 years later, a strange muggle stumbles upon Hogwarts, Harry is consumed up by guilt over Sirius and Cedric, a self-destructive Draco is trying to survive the task he was given by Voldemort, and Snape is left to pick up the pieces. (Severitus with a twist).