Decca lives in the year 2142. Her world is perfect, there is no pollution, no wars, and most importantly, no criminals. That's because if you're ever caught breaking a law, no matter how small, you're sent straight to the Underground. Of course, there's little chance that she'd ever end up in that hole in the ground over 200 feet down. When you're as rich as she is, everyone loves you. Until the day where she accidentally leaves her keys behind in a secret cave she and her best friend visit. Now she's in the Underground, that underground world made by criminals and run by criminals. Here she finds strange allies and enemies, discovers family secrets and fights with the constant knowledge that she can never go back.