In a world devastated by a series of alien invasions, humanity faces a deadly threat that changes life as we know it. After the first wave of attacks left Earth in darkness, the second wave swept away millions with a natural disaster. The third wave showed no mercy, as a lethal virus spread rapidly and wiped out much of the population. However, the worst was yet to come: the fourth wave consists of a covert invasion, where the aliens take control of human bodies, leaving the few survivors in a struggle to discern who their true allies are.
In this grim landscape, we meet Cassie Sullivan, a teenager who has lost her family in the chaos and has become a lone warrior in this new reality. With her younger brother missing, her mission is to rescue him at all costs. Along the way, she encounters other survivors and grapples with whether to trust them or to follow her instinct of distrust.
As a battle unfolds between humans and their invisible oppressors, Cassie must navigate a world filled with betrayals and difficult choices. Survival becomes a race against time, as she learns that the only way to defeat the aliens is by joining forces with others who, like her, risk everything for a future. The fight for humanity has never been so intense and desperate.