Moments after the catastrophic meltdown of ECHO-7 had begun, power plant workers immediately took their coworkers injured by the blast to the infirmary. Nurses Why Effy and Sofia Smith work tirelessly to treat all workers affected by the explosion so they can safely evacuate the building, however one patient is in critical condition after barely surviving the blast inside the reactor room.

A sudden boom plunges the infirmary into darkness. Effy and Sofia awaken to the aftermath of another explosion in the power plant. To their shock, the infirmary is destroyed and all patients are missing, including the patient most severely affected. Confused by the situation, both nurses take care of one another, trying to escape ECHO-7.

As they try to escape, Effy and Sofia witness a horrific site. Their patients are still inside the power plant, submerged in a swarm of monstrous parasites that infest their bodies. At the centre of the swarm is the critically-injured patient, sensing the presence of the nurses and commanding the swarm to hunt them down.

With an army of infected after them, Effy and Sofia attempt to hide deeper in the abandoned power plant’s halls, unaware that a parasite has latched onto their uniforms undetected...