A family of three, Ray (Alexander Skarsgård), Claire (Andrea Riseborough) and their daughter Zoe (Emily Alyn Lind), have taken refuge in an abandoned fallout shelter shortly after the Air Force begins bombing the civilian population of their town.

The family has difficulty coping in their cramped environment but manage by having a set of rules, such as always keeping calm and never leaving the shelter.

Claire kills the rat but in the process, Ray accidentally knocks over one of their lamps, burning a wooden table.

Later they discover that the smoke has left ash covering their shelter hatch, making their hiding place visible.

Claire and Ray go to the surface to cover and hide their shelter but Zoe, using a homemade periscope, spots a humanoid figure in the distance.

In a flashback to the beginning of outbreak, Ray, Claire and Zoe drive along a highway fleeing their town, Kingsville, only to be stopped with many other people by the CDC.

Claire and Zoe manage to escape through the air duct but Ray is caught and disappears, followed by a spatter of blood.

Breathers, actually American soldiers wearing night vision goggles and re-breather packs, surround them with weapons drawn.

He incapacitates three more soldiers, demonstrating remarkable physical strength and agility, and is shot multiple times before falling.

Before he is able to kill Claire, a transformed Zoe appears and exposes the soldier to the air by removing his re-breather, infecting him.

Daniel Kurland calls it "a very promising, controlled debut feature from Matt and Ross Duffer."