I thought about it for a moment, but there was no trick to it – the answer was obvious. 'The fact that she hadn't become a vampire.'

'Which means…'

'Which means?'

Iuda sighed. 'It's really no fun for me if you can't be bothered to work it out for yourself.' I looked at him blankly. 'You concluded that Dominique had not been with me because if she had been with a vampire she would have become a vampire,' he explained, like a schoolteacher.

I don't know whether I had been dull-witted or whether it was a conclusion that I wanted to avoid coming to, but now Iuda had brought it to a point where I could not ignore it. I sank back on to my seat. Could it have after all been Domnikiia that I had seen with Iuda at the window and not Margarita? Of course she had not become a vampire; Iuda had no ability to make her into one. She could have sucked every last drop of blood from the wound in his chest and it would have had no effect.

But she had believed that it would. Had she awoken that morning with exactly the same sense of surprise that I had later felt, as she discovered there had been no change in her? Had she found to her horror that she could stand comfortably in the bright morning sunlight and begun to cry as she realized that it meant she would still one day die a mortal death? She would have had to think quickly to then pretend that it was Margarita that I had seen. No, that was impossible. She must have decided to say it was Margarita beforehand. Either Iuda had told her to, or they had planned it together. There had been a great deal of careful choreography to ensure that, watching from across the square, I only ever saw Domnikiia from behind. Had Margarita known about the plan? Domnikiia had seemed genuinely shocked when we had found Margarita's body. Genuinely? How could I now regard anything about her as being genuine? A woman who would gladly become a vampire would hardly baulk at the death of her best friend being a part of the process.

It could not be true, and yet I could not see any fault in it. I myself had been sure it was Domnikiia that I had seen with Iuda right up until the point I had discovered she was not a vampire. Now I had a better explanation for that. Was I really fool enough to mistake Margarita for Domnikiia just because their hair was similar – I who knew every inch of Domnikiia's body? There must have been something more that I had seen, without consciously registering, that had told me it was Domnikiia, and now I knew it to be true. All her sorrow and anguish in the days that followed had been very convincing, but then, that was her speciality. I heard Domnikiia speaking to me, but she only repeated one whispered word over and over. How much she must have been laughing to herself when she had first said it to me. 'Prostak! Prostak! Prostak!'

Iuda placed a consolatory hand on my knee, saying, 'She did it for you, Lyosha. She thought she could be with you for ever.' He was standing now. At some point, unnoticed by me, he had retrieved his knife and had cut the ropes around his feet with it. I heard a shout from one of the soldiers guarding us to the other, but he was too late. The other had momentarily turned his back on us and Iuda was now behind him. A brief stroke from Iuda's toothed blades across his neck and he fell to the ground, the pure, white snow around him sullied by an ever-growing stain of red as blood haemorrhaged from his wounded neck, unhindered by the grasping of his dying hands.

The other soldier had raised his musket, but had been hesitant to fire while he might hit his comrade. Now he fired, but it was too late. Iuda was on the move again, keeping low and changing direction again and again. I set off in pursuit. The remaining guard did likewise, some paces behind me. The rest of the camp, consumed by their preparations for departure, did not at first notice what was happening, but soon our shouts alerted them to the fugitive. Those who threw themselves in Iuda's way offered little impediment to him. He was far more brutal and effective with his knife than any vampire could have been with its teeth. Some men tackled him with swords and bayonets, but he showed no fear, and though some of the blades hit their mark, he seemed to show little discomfort either. None of the wounds was deep enough to cause serious injury, and while posing as a vampire he had clearly learned to control his pain – along with so many other feelings – lest his humanity should be discovered.

We were now beyond the edge of the camp, almost at woodland in which Iuda could easily hide himself. The guard who had been pursuing a little way behind, younger and fitter than I was, had now caught up and overtaken me. Having discharged his musket, he had found no time to reload, and so now had only his bayonet as a weapon. He was within striking distance of Iuda when Iuda stopped and turned. The soldier had no time to stop himself. He had not been aiming his bayonet and so it glided harmlessly past Iuda's side. As he turned, Iuda brought forward his hand and the soldier ran straight on to Iuda's knife. It penetrated just below his breastbone, embedding itself deep behind his ribcage. With the force of the blow, the soldier was lifted off his feet, his back arched in agony and his limbs splayed out limply as life began to retreat from them. With a jerk of his arm, Iuda threw the man off his knife and I heard the tearing, rasping sound of its teeth making the wound even greater on exit than it had been on entry.

Iuda turned and continued to run, but I was already upon him. I launched myself towards him and grabbed him around the waist. We both fell to the ground and my face was filled with snow, blinding me. I knelt up and wiped the snow from my eyes, just in time to see Iuda's hand scything towards me, the toothed blades presented, not to stab but to slash. I flung myself backwards, flicking my head away from him. As I fell, I felt a searing pain in my left cheek where the blades connected. I fell to my back, breathing deeply, and noticed as I breathed that air was coming in through my wounded cheek as well as through my mouth.

I pushed myself up in preparation to avoid Iuda's next blow, but it did not come. A shot rang out from behind me, hitting Iuda in the arm. He turned and fled into the woods, leaving me to live with the misery that he had created for me.

CHAPTER XXXI

THE WOUND TO MY CHEEK WAS NOT AS SERIOUS AS I HAD FIRST thought. The cold weather became a brief friend as it numbed my face while the surgeon closed it up with a suture. I went back to Lieutenant-Colonel Chernyshev to tell him what had happened.

'Escaped?' he thundered.

'I'm afraid so, sir,' I replied.

'I'll have those guards flogged.'

'It's too late for that, sir.'

He glanced up at my face and understood. 'I see,' he said. 'Well, it's only one man, I suppose. All a bit of a waste of time, though.'

'Bonaparte's move south is a ruse, sir. The prisoner told me. The real crossing is to the north, at Studienka.'

'That's something at least. So you'll soon be joining us in action there then?'

'No, sir. I'd like to pursue the prisoner.'

'Is he worth it – just one man?'

'I believe so,' I said.

'Well, I suppose you people know your job. I can't lend you any men.'

'I don't ask for any, sir. Just a French uniform, if you have one.'

'We have dozens. Lieutenant Mironov, see that he gets what he needs.'

Mironov provided a dragoon uniform and a horse and some provisions, and I was soon heading out of what remained of the breaking camp. At first, I had to make my way alongside the advancing Russian troops (fortunately, I had not yet changed into my new uniform), but soon I headed off to the north of their path and the sound of marching faded behind me.

The only trail that Iuda had left was that he had planned to cross the Berezina with Bonaparte at Studienka. It was quite possible that this had been a lie, or that he would now change his mind, but my only option was still to try to intercept him there. I had not had time to properly consider what Iuda had said to me, but now as I rode through the quiet, frozen woods, I began to think.