As I spoke, the doctor touched my arm, and signed to me to look in front of us. The moon was partially obscured by thin clouds, but there was light enough for me to see two figures ahead, one skulking in the rear of the other, and keeping in the shelter of the houses. The first one walked boldly along in the middle of the road, a large figure wrapped in a long cloak; the stealthy form was not quite so tall or broad, but more agile and fleet of foot. It was the peculiar movements of the latter that had attracted the physician’s notice.

“Watch them,” he said in a low voice; “that fellow behind gains slowly but surely on the other, who is apparently unconscious of his pursuit.”

“If I ever saw a murderer and his victim, I see them now,” I replied in as low a tone; “let us give the alarm.”

The doctor shook his head. “Not yet,” he said; “rather follow and see the upshot of it. There is something familiar to me in the bearing of the taller man.”

I was conscious, too, of recognizing a certain familiarity of outline. Slipping into the shadow, we followed in the wake of the pursuer and pursued. We kept at some distance in the rear, that our footsteps might not be noticed; and the strange procession continued for some distance without the stealthy spy showing any signs of a malicious purpose. Our road lay through a lonely quarter of the town, and we had encountered no one as yet, so that our interest was centered on the two before us. The tall man in front was going straight towards the section of the city occupied by the Streltsi. In a quarter of an hour, we turned into a deserted lane, narrow and so shadowed by the high walls on either side, that not even the struggling light of the moon could penetrate it. It was here that we heard the sudden sound of a struggle in front of us, and dashed forward to the rescue. I almost stumbled over the two rolling on the ground, for I could barely discern them in the darkness; the larger man had evidently been tripped up by a sudden assault from the rear, and was beneath. I seized the other by the collar, dragging him off with difficulty, for he seemed determined to finish his fiendish work. His victim lay for a moment motionless.

“Is he injured?” I asked in French, of Von Gaden, as he knelt beside him. But as I spoke, the stranger recovered sufficiently to raise himself.

“I thank you for your promptness, M. de Brousson,” he said. “You were in the nick of time; the villain’s knife was at my throat.”

It was Peter Lykof. Recovering from my surprise, I asked him if he was free from injury.

“A trifle scratched and a little shaken,” he said calmly, rising with the doctor’s help. “It is a shock to a man’s nerves to be suddenly choked and thrown down. Who is the rascal?”

“We shall need more light to see,” I remarked carelessly, meanwhile keeping my knee on the fellow’s chest and my pistol at his head. “Have you a bit of cord there, Dr. von Gaden?” I added. “If we can tie his hands and disarm him, it will be easy to take him home for safe keeping.”