Northwest Smith rescues Shambleau running from murderous Martians, but murderous in a way he doesn't understand. He takes responsibility of her and promises not to let her out of his home.
He sleeps at night, choking in rapture and revulsion until morning. He tries to feed her but she refuses to eat. He thinks he sees her hair move beneath her turban.... With the light blocked, she feeds on his psychic energy.
His buddy, Yarol, checks on Smith, but Smith doesn't want to leave Shambleau. Yarol does what's necessary to free Smith even as Yarol's attacked. Smith has a hard time shaking himself free.
This isn't just a metaphor for sexuality as Del Rey astutely points out below, but all things that enthrall a man's mind. He's never the same. Sexuality, though, is the primary concern. Moore connects Shambleau to Medusa, the Greek woman who turned men to stone.
"Here for the first time in the field, we find mood, feeling, and color. Here is an alien who is truly alien.... Here are rounded and well-developed characters.... And--certainly for the first time I can remember in the field--this story presents the sexual drive of humanity in some of its complexity."--Lester Del Rey on "Shambleau"
"Catherine L. Moore is rightly regarded as one of the most remarkable stylists in the SF field. She once described the basic thread of her fiction as, 'Love is the most dangerous thing.' "--David Drake
C. L. Moore on how she constructed stories, "Shambleau" in particular.