Cora and her friends have escaped the Kindred station and landed at Armstrong -- a supposed safe haven on a small moon -- where they plan to regroup and figure out how to win the Gauntlet, the challenging competition to prove humanity's intelligence and set them free. But Armstrong is no paradise; ruled by a power-hungry sheriff, it's a violent world where the teens are enslaved and put to work in mines. As Nok's due date grows closer, and Mali and Leon journey across space to rescue Cassian, the former inhabitants of the Cage are up against impossible odds. With the whole universe at stake, Cora will do whatever it takes, including pushing her body and mind to the breaking point, to escape Armstrong and run the Gauntlet. But it isn't just a deranged sheriff she has to overcome: the other intelligent species -- the Axion, Kindred, Gatherers, and Mosca -- all have their own reasons to stop her. Not knowing who to trust, Cora must rely on her own instincts to win the competition, which could change the world -- though it might destroy her in the process.