It Knocked Three Times

In the shroud of night I weave through slumber,
shaken by a rapping upon my door.
Three times, with a pause in between,
but each like a hammer against my eardrum.
Upon rising from my bed, I pause to listen...
Is it gone?
No, the knocking starts again.
Another set of three, the pause seems longer this time.
Sleep knocks upon my head as I descend the stair,
Sandman's seed planted in my eyes.
Silence?
Perhaps my uninvited guest has given up...
But no, the banging rages again.
Thrice, with an eternity between each.
Who is this stranger at my door?
What business does he have at this hour?
Before the pounding comes again,
I fling open the door into the chilly night,
and I find nothing...