He stood at the top of the staircase and raised his voice.
"Is all well, gentlemen?" he asked loudly; but he received no answer.
"Is all well?" he cried again.
And then from the gloom emerged Inspector Frith. He had doffed his gas mask.
Sir Walter switched on an electric light.
"Nothing, I trust, has happened?"
"Nothing whatever, Sir Walter. No sign or sound of anything out of the common can be recorded."
"Thank Heaven—thank Heaven for that!"
"Though we had exhausted the possibilities of such a thing, we none the less expected gas," explained the detective. "That seemed the only conceivable means by which life might be destroyed in that room. Therefore we wore gas masks of the latest pattern, supposed to defy any gaseous combination ever turned out of a laboratory. It is well known that new, destructive gases were discovered just before the end of the war—gases said to be infinitely more speedy and deadly than any that were employed. As to that, and whether the Government has the secret of them, I cannot say. But no gas was liberated in the Grey Room last night. Otherwise a rat in a trap and birds in a cage, which we kept by us, would have felt it. The room is pure enough."
Sir Walter followed him down the corridor, and chatted with the other men also. They had left the Grey Room and taken off their masks; they looked weary and haggard in the waxing, white light of day.