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.