Fifteen-year-old Sarah resents her baby brother Toby and secretly wishes that he will just disappear. Her wish comes true when goblins kidnap the boy. Feeling responsible and guilty about his abduction, she sets forth to retrieve him, and finds herself on the adventure of a lifetime. To rescue her brother, she must sneak into the castle of the Goblin King, which is in the center of a fantastical labyrinth. But the task is easier said than done, for the maze is filled with strange creatures and mind-bending puzzles, and nothing is really as it seems.