A speaker lies awake at night, listening to the house make noises: the gutter, the roof tiles, the leaves outside. Everyone else in the family is asleep, and the clock says ten forty-four. Alone with these sounds, the speaker feels a sudden jolt of fear, imagining a scene from a horror movie where someone knocks at the door.
What makes the poem believable is how ordinary the fear is. The speaker doesn't see anything frightening, only hears it, and the mind fills in the rest. The short, plain lines and simple rhymes ("bed" and "head") give it the quick, jumpy rhythm of a racing heart. Telling themselves "it's all in my head" is a small act of self-comfort, like a child talking themselves out of the dark.
The ending releases the tension. The cause was only the autumn breeze, and the mood shifts from dread to relief, with a touch of embarrassment at having been so worried.