Warner Bros. Pictures

After the Dementor attack on Harry and Dudley, Vernon tried kicking Harry out of their house. But Petunia received a Howler that said “Remember my last, Petunia,” which mysteriously made her allow him to stay. The Howler had been from Dumbledore and it referred to the letter he had left with Harry on the Dursley’s doorstep the night Harry's parents died. That letter had informed Petunia of the charm that Dumbledore placed upon Harry that would protect him from Voldemort as long as he called Petunia’s house, where his mother’s blood resided, home.