Penguin Random House Children's UK Sorcerer in the North (Ranger's Apprentice Book 5)

Will, you are a Ranger now, protect your land at all costs. You are a fully-fledged Ranger at last, but your new land is already under threat. The Grimsdell Forest is being haunted by eerie voices and the terrifying figure of the Night Warrior. Could this really be the work of sorcery? As you battle growing hysteria and traitors, your lifelong friend, Alyss, is taken hostage. Time is running short. Do you save her or stay true to your mission?