“Arm?” cried Thresk.  “What are you talking about?”

Ballantyne looked away from the wall to Thresk, his eyes incredulous.

“But you saw!” he insisted, leaning forward over the table.

“What?”

“An arm, a hand thrust in under the tent there, along the ground reaching out for my box.”

“No.  There was nothing to see.”

“A lean brown arm, I tell you, a hand thin and delicate as a woman’s.”

“No.  You are dreaming,” exclaimed Thresk; but dreaming was a euphemism for the word he meant.

“Dreaming!” repeated Ballantyne with a harsh laugh.  “Good God!  I wish I was.  Come.  Sit down here!  We have not too much time.”  He seated himself opposite to Thresk and drew the despatch-box towards him.  He had regained enough mastery over himself now to be able to speak in a level voice.  No doubt too his fright had sobered him.  But it had him still in its grip, for when he opened the despatch-box his hand so shook that he could hardly insert the key in the lock.  It was done at last however, and feeling beneath the loose papers on the surface he drew out from the very bottom a large sealed envelope.  He examined the seals to make sure they had not been tampered with.  Then he tore open the envelope and took out a photograph, somewhat larger than cabinet size.

“You have heard of Bahadur Salak?” he said.

Thresk started.

“The affair at Umballa, the riots at Benares, the murder in Madras?”

“Exactly.”

Ballantyne pushed the photograph into Thresk’s hand.

“That’s the fellow—­the middle one of the group.”

Thresk held up the photograph to the light.  It represented a group of nine Hindus seated upon chairs in a garden and arranged in a row facing the camera.  Thresk looked at, the central figure with a keen and professional interest.  Salak was a notorious figure in the Indian politics of the day—­the politics of the subterranean kind.  For some years he had preached and practised sedition with so much subtlety and skill that though all men were aware that his hand worked the strings of disorder there was never any convicting evidence against him.  In all the three cases which Thresk had quoted and in many others less well-known those responsible for order were sure that he had devised the crime, chosen the moment for its commission and given the order.  But up till a month ago he had slipped through the meshes.  A month ago, however, he had made his mistake.

“Yes.  It’s a clever face,” said Thresk.

Ballantyne nodded his head.

“He’s a Mahratta Brahmin from Poona.  They are the fellows for brains, and Salak’s about the cleverest of them.”

Thresk looked again at the photograph.

“I see the picture was taken at Poona.”