Tuck heard the sound, and his stomach swooped. It was like the floor fell out from under him in an instant. "Who the hell are you?" he asked, backing up quickly now, eyes widened in alarm. How could they know that whistle unless they had been taught. And who would have taught these random kids he didn't know, except his enemies. Oh god, they were somehow related to John. Or worse, Guy. "Who taught you that whistle!?" He reached for his phone and pulled it out as Brook raised her hands in surrender.
"Wait!" Brook hissed, worried they were about to be attacked because the mood had changed so suddenly. "Our Pa taught us!"