Therefore, when Roger went upstairs, his report made his cousin nod approvingly. Roger had done all he could to avert danger if the rats had been taken ignorantly by some idiot who might let one or more escape and spread disease germs.
With his story told, Potts was busy doing what Grover had ordered as one way to secure clues: a motion picture camera using non-flam film, flashbulbs of the latest type, tripod for time exposing, and both wide-angle and micrometric lenses, to give large views of big spaces or vastly magnified details of practically invisible things, formed the kit that the handy man worked with.
Because he had used his wit Grover had no orders for Roger as the firemen, police and officers departed.
Nothing could be done until Potts developed his “takes” so they could be run in the laboratory screening-room.
Grover, in his small, private “thinking den,” would want to be left to think out and separate all the mysteries, so that he could get to the heart of the affair and thus decide what to do about it.
Alone, wide-awake, with the dawn just beginning to lighten the skylight in the roof over his stock-room, Roger stood thinking.
He knew that if the small, partitioned space set aside for Doctor Ryder had held clues, Grover would have told him.
The germs supposed to have been injected into rats the night before could not have produced much effect that past night. The doctor had not felt that he had to observe, personally, as he would have done later.
Instead, automatic “observers” had been set up.
Inside the empty cage, a dictagraph microphone showed, fixed to the glass inside the cage top. That, Roger knew, led to a device like the seismograph which registers earthquake tremors. Its purpose was to show, by the vibration of a pen across a moving tape, when the rats developed any unusual excitement or stress, which was not expected but was provided for in that way.