Anyone who has hurried down a dark staircase will recognize the feeling in this poem. The speaker is convinced a monster lives under the stairs, and the proof is simple: they have heard him. He even sneezes hard enough to shake the house, which is a funny detail that makes him seem both huge and oddly human.
The speaker's fear shows in the counting. Each step, from one up to seven and on toward eleven, is a small act of courage, and the question "Did the monster hear me open the door?" keeps the tension going. The speaker holds their breath and hopes the monster has left town, which sounds hopeful but also a little unsure.
The mood is playful spookiness. Short, bouncy rhymes like "hairy" and "scary" feel like a childhood chant, so the fear never gets too heavy. The last lines turn to the reader, daring us to try the stairs and watch out, as if the monster might be waiting for us next.