“Not much—but if I am, I will stay, just the same.”

“Then set up that sound camera, with film, so you can take in every foot of this partitioned room. Be ready, and if the voice comes again, switch on, for continuous takes.”

“You think—anybody is hiding?”

“No. But a voice means something vibrating. I could not locate anything. The camera might do so.”

He went down, to give Potts some instructions and took over the monitor’s post while the handy man executed his order, which was to mix fresh developers and fixing baths, and to be ready for whatever Roger caught.

Doctor Ryder, helpful and desiring, as he made plain, to take away Roger’s sense of fear by explaining how the Far East made so uncanny a manifestation by mental powers, handed him the can of non-flam negative so that Roger lost no time in “threading up” and getting all ready for his duty.

Alert and steady, in spite of his chill of nervous uncertainty as to what might come next, Roger heard, seemingly from a corner of the small room, a thump.

“Start it!” gasped the man beside him.

But when two minutes of time had run out the film in his magazine and nothing more had come, Roger disappointedly took the film into the dark room and changed the magazines, hurrying back.

Half an hour later, with nothing to break the tedium, the next amazing development came. Potts, in the dark-room, shouted, and tore out into the light, waving a damp strip of film. He had developed the film on the chance that the thump had caused some change.