They were discussing the many contradictory and unexplainable points when Potts called, from the darkroom:

“Hi, Rog’—come quick!”

As soon as his eyes were accustomed to the dull rosy glow after he passed the light-trap, Roger saw Tip clipping non-flam film positives to drying drums.

“What have you got, Tip?”

“Look!”

Potts snapped a strip in place in a vision tunnel: Roger applied his eye to the lens, and saw, enlarged on the viewing-plate, what appeared to be the edge of a cellar step. With side-lighting, magnified ridges and depressions in dust looked like a range of hills and vales.

“It was a snake!”

“A—did you say ‘snake’?” Roger gasped, “How do you get that?”

Potts changed films under Roger’s gaze; an enlarged wide-angle of several steps was before his eyes, and the snake-slide of some body that had dragged across just the step-edges, and had made no track of hand or foot on the level of the steps showed!

“It certainly looks like something that creeps, Tip.”