A meteorite impact on a distant, inhabited planet brings with it a terrible secret. Hidden within the celestial stone are aggressive alien creatures capable of extremely rapid evolution. Their arrival plunges civilization into ruin, leaving humanity on the brink of extinction.

The story centers on John, a young man who has lost everything, including his sister Emma, in the alien onslaught. Desperate and suicidal, he wanders a desolate wasteland with a small group of other survivors. When they detect a mysterious signal, a faint hope draws them toward its source, despite John's suspicion it could be a trap. The group falls victim to a landmine explosion and a subsequent alien attack, from which they are rescued by a heavily armed military group and taken to a fortified underground shelter called Jericho. However, this sanctuary is not what it seems.

Jericho is a twisted survival camp run by the charismatic but deeply unstable Leon and his second-in-command Norman. John learns that his benefactors have no intention of simply protecting the remaining population. To fight the monsters, the soldiers of Jericho have begun a process of forced evolution, feeding captured humans the flesh of the aliens. This gruesome meal is a gamble, causing horrific body horror and agonizing death for most, but for the rare few who are "compatible," it triggers a terrifying transformation into an Adapter—a powerful human-alien hybrid capable of fighting the invaders on equal terms.

Trapped in this violent and oppressive environment, where captives are used as disposable test subjects, John must fight for survival. Refusing to be a pawn, he is forced to adapt. The initial story arc primarily takes place within the claustrophobic and brutal confines of the Jericho bunker, establishing its system of power and the horrific price of power. As the narrative progresses, the world expands beyond Jericho. John encounters a wider, even more shattered world filled with religious zealots who worship the aliens as fallen gods and other factions of desperate survivors struggling to make sense of the new world order.

Eventually, John undergoes the grueling process of adaptation himself, gaining the monstrous strength necessary to challenge both the alien threat and the oppressive human forces that seek to control him. The story follows his journey from a broken man who has lost the will to live into a determined force for survival, exploring humanity's capacity for cruelty and resilience in the face of cosmic horror.