Either the intruder was hesitating because of Roger’s silence or he was very quiet in his actions.
Roger, equally quiet, was extremely active. He had unlaced and had slipped off his shoes at once. On stocking feet he tiptoed to the large gas outlet set into the wall for use with Bunsen burners or gas heaters used in experiments where a regulated heat was needed.
This he opened, full, by turning the valve one half a revolution.
Darting swiftly away from its low, humming release of a heavy flow, he ran quietly across to the thermostat on the wall, connected into the fire alarm and release system. Under it was a manual lever, one to be operated by hand, in any emergency where the thermometer failed.
Swiftly Roger threw this on, and with his handkerchief tied over his nostrils and back of his head, for already he smelled the gas of the opened outlets, he swarmed up the telescope.
The house-lighting gas, he knew, would be held down, running to the lower floor down the stairway, and the amount released would be enough to stupefy quite soon. Even if the adversary climbed the stairs, he would be in a bath of the sleep-inducing sulphuretted hydrogen.
With his arms and legs helping him rise, Roger clambered up the inclined metal barrel of the telescope. At the top, above the flow of smother-gas to kill fires, he paused, listening.
Not a sound.
To the roof he clambered, and sat on the coaming of their skylight, looking down, waiting a few moments in case the other tried to come up.
Below him all was silence.