Almost nothing happens in this short poem except one repeated glance. A speaker watches a woman walk ahead of them, and the only thing they can focus on is the sway of her behind. The words "swinging" and "behind" keep coming back, shuffled into slightly different orders, as if the speaker's mind is stuck on a loop and can't look at anything else.
The one image that breaks the pattern is the lantern. A lantern swings gently, gives off light, and draws the eye in the dark, so the comparison suggests the speaker finds the movement glowing and hypnotic. It may also hint at warmth, which would fit the title, "Hot House."
The mood is playful, fixated, and a little steamy. The repetition acts like a rhythm, almost a rocking motion that mimics the swing it describes. Whether the speaker's gaze feels admiring or intrusive is left for the reader to decide.