shall go and inquire, if they will permit me to do so. Oblige me by staying here a few minutes until I call my daughter. I do not want our poor friend to be alone until he leaves us."
"I will stay here for the present. But don't let Mary be called if she is sleeping, and turn in yourself for a few hours now."
"I have slept off and on."
Sir Walter left him and ascended to the corridor. Already light moved wanly in the windows.
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
