He is there.

Yesterday, upon the stair,
I met a man who wasn’t there
He wasn’t there again today
I wish, I wish he’d go away...

When I came home last night at three
The man was waiting there for me
But when I looked around the hall
I couldn’t see him there at all!
Go away, go away, don’t you come back any more!
Go away, go away, and please don’t slam the door... (slam!)

Last night I saw upon the stair
A little man who wasn’t there
He wasn’t there again today
Oh, how I wish he’d go away