Caterpillar

Anyone know what kind of caterpillar this is? I found it this morning, inside our house, on the wood floor near the front door. As that didn't seem like a good place for it to be, I picked it up and took it outside. It didn't seem to want to stay in my hand and sort of tossed itself onto the wet leaves in front of the house. Having no idea what sort of location would be appropriate I just left it alone, and it promptly squirmed under one of the oak leaves. I should go look and see if it's moved on!

Please tell me if you know what it is!

Edit - A friend who is a naturalist - whom I finally asked - says it's the caterpillar of a moth called a Mottled Prominent.