" Far ahead, the others neared the bridge that led to the fifth and final tower. And what then? Janner wondered. What happens when there’s nowhere left to run? Just as the boys reached the bridge to the third tower, the ground shook. The trolls were only a few feet behind, and one of the beasts had pounded its fist on the tower floor. "

― Andrew Peterson , North! or Be Eaten (The Wingfeather Saga, #2)