Harry and Hermione Riddle

Harry and Hermione are having a normal holiday after the war. Well, as normal a holiday you can have as a wizard. They're both going back to Hogwarts to redo their last year. A few days before the start of the school year they are invited by Gringotts Wizard back to do an inheritance test.

What happens when they find out they aren't who they think the are and when they horrible things people have done?..