Well, it couldn't have lasted forever. He just wasn't all that good at fooling mortals, not when it really came down to it. That's why he so often simply hunted and killed before they could react to his presence. Even back at the very beginning, when Marius had first turned him, he hadn't been that good at the deception of being a normal human boy. So he dropped the charade right then and there.
The vampire laughed, and this time, the light gleamed off his sharp, wickedly pointed and very white fangs. Almost leisurely, he reached out and grabbed the young man's hands, holding him still for a long, agonizing moment before drawing him inevitably closer to him. He was far stronger than any human, and certainly more than anyone of his build had any right to be.
"I met your friend when he arrived..." His voice was almost dreamlike, but his eyes were sharp and focused on Rudolf. "He found me... frustrating. He couldn't do anything to me, you see."