Peter had heard the scream in his mind. When it came to Claire, there was no time wasted in answering that call. The time in between when he received the call and when he appeared on the scene was spent grasping Nathan by the arm, and then using his clairvoyance to find where Claire was.
"Claire!" was the scream that tore from Peter's throat as he materialized. Fear was gripping him, but that was quickly overcome by rage as he saw the thing that was once Sam Winchester holding his niece.
Super speed, heightened reflexes, and fury enough to fill one of the circles of Hell were all on Peter's side as he rushed at the demon, one hand stretched to push the knife away from Claire's throat as the rest of him barrelled into Sam, trying to knock him aside, mentaly screaming at Nathan to help Claire.
"You want to carve someone, pretty boy?" Peter growled, scrambling to hold onto the wrist weilding the knife. "Try me for size."