There was nothing to be heard save the wind and the rain.

Where, then, could his father be?
If he wished to enter the Hall he would not attempt to do so by one of the windows, for had he not been present when Raffles Haw had shown them the precautions which he had taken?
But then a sudden thought struck Robert.

There was one window which was left unguarded.

Haw had been imprudent enough to tell them so.

It was the middle window of the laboratory.