The town of Welby is surrounded by a high wall, erected in long-forgotten days when people remembered their magic and Immortals walked the earth. Oren and Carah grew up together in Welby, but when Oren makes a mistake that could get Carah exiled, he has no choice but to climb over the wall and enter the unknown world beyond, following a river and looking for a necklace. The world is full of creatures and people Oren never dreamed of, but friend and foe alike offer him the same advice: Don't follow the water. Oren's journey leads him to an impossible castle, and inside, Oren finds the necklace, and a reason to never go back home.