Monster Approaching

My dreams were twisted and troubled,
And I was wrestled from my sleep,
The blankets were wet and tangled,
In a heap around my feet.
I looked through the doorway,
And lumbering through the night,
Was the worst kind of monster,
Bulging with its awful might.
I vacillated on a course of action,
Run? No, instead,
I hunkered down and cowered,
With the blankets draped across my head.
And as it approached me murderously,
I sensed its sad defeat,
For everyone is aware that,
Monsters can't bite through a sheet.

This is a universal rule - see a monster, duck under the sheet - they can't bite through them.