Spider plays dead

I never kill spiders. I found a spider in my bedroom. I thought it was dead at first but when I put a glass over it and then slid a piece of card underneath it crawled on, dragging one of its legs behind it. Then it turned on its back where it stayed, its legs all screwed up. I thought it had definitely died.

A bit later I took it outside and put it in with some plants and it turned over again and ran off!

Jane