All You Zombies

Then I glanced at the ring on my finger.
The Snake That Eats Its Own Tail, Forever and Ever.
I know where I came from–but where did all you zombies come from?
I felt a headache coming on, but a headache powder is one thing I do not take.
I did once–and you all went away.
So I crawled into bed and whistled out the light.
You aren't really there at all. There isn't anybody but me–Jane– here alone in the dark.
I miss you dreadfully!

--All You Zombies,  Robert A. Heinlein