In a small Colorado town, chaos erupts as a strange illness rapidly spreads among its inhabitants, transforming them into aggressive, zombie-like creatures. Corporal Sarah Bowman, a soldier stationed at a local military base, and her team are mobilized to contain the situation. As the infection spirals out of control, Sarah, along with her fellow soldiers—including wisecracking Private Salazar and the inexperienced Private Bud Crain—struggle to discern the cause of the outbreak while maintaining order amidst the growing panic.

Against this backdrop of terror, the survivors quickly realize that standard military protocol is ineffective against the escalating threat. With the town quarantined and communication lines breaking down, Sarah and her comrades find themselves cut off from the outside world. As they delve deeper into the town's chaos to find Sarah's mother and brother, they come face to face with the horrific extent of the epidemic. The group must adapt and improvise, forging unlikely alliances with remaining civilians, including the rebellious teenager Nina and her boyfriend, in a desperate bid to find a safe haven from the relentless, undead horde that seems to learn and adapt with each passing moment.