Hide and seeker

Something is wrong with twelve-year-old Zee, who has returned after a year's absence; nobody knows where he was or what happened to him, but now he is distracted and violent, freaking out when he sees his friends, Justin, Nia, and Lyric, playing an odd game of hide-and-seek, and talking wildly about some danger that is approaching--and soon his friends are pulled into a shadowy world ruled by a monstrous, shape-shifting Seeker, forced to play a terrifying game of hide-and-seek where they will have to confront their worst nightmares in order to find their way home.