“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.

“You’ve done your duty, and I am beyond measure thankful that no evil has overtaken you.  What can now be prepared for you in the way of food?”

They thanked him, and declared that in an hour they would be glad of breakfast.  Then Sir Walter went to his own apartments, rang, and gave the needful directions.  He joined Mary soon afterwards, and she shared his thanksgivings.  She was already dressed, and descended immediately to Dr. Mannering.

Henry Lennox also appeared soon afterwards.  He had already learned from Fred Caunter that the watchers were safely through the night.

Chadlands was the scene of another inquest, and again a coroner’s jury declared that Septimus May, as his son before him, had died by the Hand of God.  Later in the day the dead man was conveyed to his own parish, and two days later Sir Walter and Mary, with her cousin, attended the funeral.

Meantime, the detectives began their serious work.  They proceeded with system and upon their own plan.  They omitted to question not the least of the persons who dwelt at Chadlands, and inquired also privately concerning every member of the house party there assembled when Tom May died.  Into the sailor’s private life they also searched, and so gradually investigated every possible line of action and point of approach to his death.  The cause of this they were content to disregard, arguing that if an assassin could be traced, his means of murder would then be learned; but, from the first, no sort of light illumined their activities, and nothing to be regarded as a clue could be discovered, either in Tom May’s relations with the world, or in the history and character of anyone among the many who were subject for inquiry.