The soldier came to the alert like a terrier at a word, but his straining ears could not distinguish a sound beyond the laboured ticking of the hall clock beyond.
"I hear nothing," he muttered to himself.
He had not long to wait. Half-way up the stairs something snapped off like the miniature report of a toy pistol. Before the sound could translate itself to the human brain another louder discharge had swallowed it up and out of its echo a crackling fusillade again marked the dying effects of the scattered explosive.
At the first crack Carrados had swept aside the screen. "Light, Parkinson!" he cried.
An electric lantern flashed out and centred its circle of brilliance on the stairs opposite. Its radiance pierced the nebulous balloon of violet smoke that was rising to the roof and brought out every detail of the wall beyond.
"Good heavens!" exclaimed Colonel Aynosforde, "there is a stone out. I knew nothing of this."
As he spoke the solid block of masonry slid back into its place and the wall became as blankly impenetrable as before.
"Colonel Aynosforde," said Carrados, after a hurried word with Parkinson, "you know the house. Will you take my man and get round to Dunstan's workroom at once? A good deal depends upon securing him immediately."
"Am I to leave you here without any protection, sir?" inquired Parkinson in mild rebellion.
"Not without any protection, thank you, Parkinson. I shall be in the dark, remember."
They had scarcely gone when Dr Tulloch came stumbling in from the hall and the main stairs be-
