When I turned off the light last night Molly was curled up beside me with her front paws on my forearm. She had been purring loudly, but as she began to doze off the purr had subsided to something more felt than heard. I was also just beginning to drop off when a bird hit the window, which leads to the following two observations:
Cats can move really, really fast.
When they do that they use their claws for traction.
I eventually did get to sleep. Who knows where Molly was.