Don't Answer the Third Knock

The rules were simple:

One knock, ignore it.

Two knocks, ignore it.

Three knocks—whatever you do, don't answer.

I laughed it off. Urban legend nonsense.

Until midnight came, and I heard the first knock.

Then the second.

At the third, the doorknob rattled. My dog whimpered under the couch.

I peeked through the peephole.

No one was there.

But when I turned around, muddy footprints led from the door... directly to my bedroom.