So we looked. And this is what we saw: Serena standing above us, in a space between the branches, where a moment before there had been only sky. The darkness around her was latticed with oak leaves. She was standing in the air, in that white dress, her hands stretched out beside her, her toes pointed downward. One rope of black hair cut across her body like a sash, letting in the night. Her eyes were closed, her face as flat and remote as the moon, a closed system that needed nothing, that could expose itself to you completely, without tremor, because you’d never get close to reaching it. Levitation is good for the soul, she had told me once. She drifted a little higher. I watched her, sure that if I blinked, she’d disappear, reveal herself as a dream, an illusion, a fata morgana. But her dress was flapping in the breeze, a soft slap slap slap against her legs. Was she dizzy, up there, higher than any of us had ever gone? Was her stomach churning? Did the altitude make a difference when you were no longer tethered to the earth?

“Serena,” I whispered, and she looked down at me, though she couldn’t have heard me. She tipped slightly in the air, and held up a small white hand, a miraculous hand, like a bird. Her wrists shone bare, almost blue. Her protection cords were gone. When had she cut them? She looked so quiet there in the sky, not angry or hurt or sad at all.

This is the thing. This is the thing I need to see, to understand. This is the crux of it all; I should not look away. And yet I want to tell you that the fata morgana is a complex superior mirage that occurs when light passes through a series of slices of air of different temperatures. Different temperatures mean different densities, and so an atmospheric duct is created, and so as the light comes through, it bends: refraction. The mirage appears when our eye-brain sees the kinked light and assumes it’s coming on a straight path. In a fata morgana, the light reflecting from a distant object bends downward, but your eye doesn’t know that, and so your brain raises the object in question into the air. It happens most often over water—sailors have seen floating cities, upside-down ghost ships (the Flying Dutchman is a famous fata morgana), mountain ranges, spaceships—but it can appear anywhere.

I also need to tell you that the phenomenon is named after the Arthurian sorceress and shapeshifter Morgan le Fay, the deathless nymph, who is capable of flight, who has something of the siren in her, who is said by some to live in a levitating castle above Mount Etna, from whence she beckons travelers. Morgan, who sought Lancelot’s bed even as she sought his undoing, who was both healer and destroyer.