Mrs. Smithson, the housekeeper, conducted Andrew Larkspur from room to room during this careful investigation of the premises; and she and Stephen Plumpton alone were present when he examined this half-glass door.
"Do you always bolt your door of a night?" Mr. Larkspur asked of the footman.
"A ways, sir."
The tone of the man's voice and the man's face combined to betray him to the skilled police-officer.
Andrew Larkspur knew that the man had told him a deliberate falsehood.
"Are you certain you bolted this door on that particular night?"
"Oh, quite certain, sir."
The police-officer examined the bolt. It was a very strong one; but it moved so stiffly as to betray the fact that it was very rarely used.
Mrs. Smithson did not notice this fact; but Mr. Larkspur did. It was his business to take note of small facts.
"Can you remember what you were doing on that particular night?" he asked, presently, turning again to the embarrassed Stephen.