From his perch on the window sill, Mjolnir took a minute to size up the scene more carefully. The back door was closed, but the cat knew that it often did not latch. He jumped down onto the porch, and nosed along the bottom of the door. He thought he detected a little 'give' when he gently pushed at it with his nose.

Good. Not latched. There was a half inch gap between the bottom of the door and the door sill. Crouching, he eased a paw, claw-side up, into the crack, dug his claws into the door as best he could, and pulled.