In chapter 6 in flush what did Noah discover

Noah and Abbey were caught hiding in the bushes. When one of the guys grabbed Abbey, he was very sorry. She'd been a biter from way back. She chomped down on the man's arm and wouldn't let go. The guy, who was bald-headed and had a big crooked nose, screamed and howled and finally let go of her. He was about to sock her when Noah stopped him with a punch to the face. They hit the dock and ran to their bikes. They had never pedaled their bikes so fast in their lives. They were afraid their mother was awake and had discovered that they were gone. But they sneaked in and went to bed with their mother apparently none the wiser.