Having escaped from the corrupt Enclave, Gaia ventures into the wasteland with her baby sister, Maya, hoping to find a settlement that's rumoured to lie in the Dead Forest. After days of travelling, Gaia is close to death when Peter, a ranger from the mysterious village of Sylum, finds her and takes her back with him. Gaia soon realises that Sylum has as many strict laws as the Enclave she fled from, but when Maya is taken from her by the ruthless village leader, the Matrarc, Gaia is forced to stay and submit to their strict social code, or risk losing her sister forever.

But Sylum is in trouble. The population is falling and the amount of women dwindling dramatically, and with a deadly fever affecting striking down anyone who tries to leave, the future is bleak for the village. Desperate to escape with her sister, Gaia is determined to uncover the secrets of the village, whatever it takes.

And when Leon is captured too, Gaia is faced with another tough choice between the boy who captured her heart in the Enclave, and Peter, for whom she can't deny her growing feelings. But when the decisions you make affect the lives of everyone around you, how can you be sure you're making the right choices?