For a few moments, there's nothing, just a placid little creek slowly winding through the woods and some fireflies twinkling. Dan's about to assume that they just saw a nightjar fly across one of the camera lenses or a trick of the light.

Then it happens again, this time more clearly and in a pair: two lanky, graceful figures dressed in white, darting between clouds of fog over the creek in leaps. They just so quickly and high that at first they seem like white deer jumping the creek, but no - they're women, ballerinas, throwing themselves in a grand jeté over the water and into the embrace of more fog. Their faces are a blur on the drone's camera, like a refraction error, and their long fingers seem skeletal as they comb the air and drag trails through the fog. They vanish into the gloom.

"Well, reckon I'm not crazy." Dan runs his hands over his face. "I'll be damned."