The speaker describes a small, everyday moment: a woman turns quickly, and her wet hair brushes his cheek. That brief touch, along with the scent and the dampness of her freshly washed hair, throws him off balance. He says it "drives his demons high," which suggests a rush of wild, restless feeling he can barely contain.
She glances back, pushes her hair from her face, and offers a small apologetic smile. He can only stare at her bright, eager expression, and the poem says this makes him "go haywire." By the end he feels like a child watching a miracle.
The question that opens and closes the poem, "Magic, isn't it?", frames the whole scene. The repetition, with its extra question mark at the end, makes his wonder feel stronger by the final line. The mood is playful, giddy and tender: infatuation shown through one ordinary, accidental touch.