Isolation

Orla palpates a cow and is seemingly bitten by the unborn calf. She informs John of the strange bite, but he dismisses her concerns and urges secrecy about the experiment. The incident hints at a dangerous, unknown parasite at work on the farm.

Dan confronts Traveller Jamie and his girlfriend Mary and tells them they must leave by morning due to the secret experiments. He warns them to keep quiet and maintain distance from the farm. The tension on the farm rises as outsiders become involved.

That same night one cow goes into difficult labour. Dan enlists Jamie's help to birth the calf, and together they manage it. The calf bites Dan during the delivery, earning his temporary gratitude, and he invites Jamie and Mary to stay.

Next day Orla inspects the calf and discovers it has fangs. When she decides to terminate the calf, its mother attacks in defense and Orla is forced to kill them both. A necropsy reveals six malformed foetuses with skeletons growing outside their bodies, suggesting an unusual and dangerous infection.

Next morning Jamie notices strange wounds on a cow, and something bites him as he passes through shallow water in the barn. The farm's mood darkens as illness and fear spread. The first inklings that the infection may be contagious reach the couple.

A police officer arrives at the farm and informs Dan that Orla is missing. The absence adds to the growing sense of danger and the authorities' concern grows.

John returns to the on-site lab to check the experiments and learns about the malformed foetuses. He discovers their cells are multiplying extremely quickly and realizes the threat could extend to humans.

Inside the Traveller caravan, Mary notices unusual behavior from Jamie as they are together. They are awakened by a creature crawling in their bed, and it quickly escapes.

John informs that the entire farm must be quarantined to prevent the creature from infecting other cows and sparking a pandemic. The quarantining order heightens tension as workers scramble to seal the farm and monitor livestock.

They begin searching for the creature but find that it is hiding in the murky water flooding the farm. Dan uses his tractor to flush it out, but instead discovers Orla's body in the water.

John takes Orla's body to the lab and finds foreign material inside a wound on her abdomen. The material shows extreme cell growth and also contains human cells, leading him to realize that humans may be susceptible to the infection.

Jamie realizes he is infected and tries to escape, but John kills him. John explains that he has killed almost every cow on the farm in his search for the creature.

They reach the barn where the final cow is kept, but the calf has already been born and escaped. John is attacked and killed by the creature while chasing Mary, and Dan survives the earlier confrontation. They continue to search for the monster.

Mary finds the calf as new creatures rupture from its body. Dan creates a diversion by making noise to lure the creature away, allowing Mary to injure it with boiling water and finish it off. Dan dies from his injuries, while Mary leaves the farm.

Four months later in Birmingham, England, Mary is pregnant and the baby is deemed healthy. In an ultrasound, a creature-like shape is briefly seen inside the fetus, hinting that the threat may not be over.