Near Christmas Eve in Spain, Manel, a lawyer and owner of a solar power business, and his wife Julia, visit his older sister Belén and her family, including her husband Mario and young son Carlos. During their drive home that fateful night, a heated discussion unfolds about Manel’s reluctance to start a family of his own, which tragically culminates in a horrific car accident resulting in Julia’s untimely death. A year passes in a fog of despair, during which Manel isolates himself in his Galician home with only his cat Lúculo for companionship, maintaining scant video contact with his sister and nephew.
As Manel grapples with his intense grief, he becomes blissfully unaware of an alarming crisis sweeping across Europe—an outbreak of a virulent virus known as TSJ. Despite the government's desperate measures to keep the truth hidden, the virus transforms those infected into highly aggressive zombies, causing widespread panic. Meanwhile, Belén's family is evacuated to the Canary Islands, but when Manel attempts to join them, the government abruptly shuts down borders and declares a national emergency. He reassures Belén to stay put, even as the army mobilizes to evacuate the remaining citizens.
While scouring for supplies, Manel witnesses a shocking scene: an infected individual attacking two police officers, leading to chaos as one officer kills the assailant before succumbing to the infection himself. After barricading himself in his house, Manel’s supplies soon dwindle, and he becomes cut off from communication, leaving him clueless about his family's well-being. During a desperate expedition for provisions, he encounters an elderly woman named Gabriela, who has been unable to evacuate due to her wheelchair. With her assistance, he manages to gather essential supplies.
That night, Gabriela mentions a radio broadcast inviting survivors to the Arousa Estuary, offering a chance for escape to the Canaries. Despite Gabriela's reservations, Manel resolves to take her by boat—a vessel he and Julia once owned. However, the harsh reality hits when he discovers the next day that Gabriela has taken her own life to avoid being a burden during his flight.
Equipped with a diving suit, speargun, and Lúculo by his side, Manel sets out towards the docks, narrowly escaping a horde of zombies that pursues him. He finds all substantial vessels either missing or inoperable. Opting for an inflatable dinghy, he attempts to navigate to Pontevedra, but soon encounters a group of ragged Ukrainian sailors, led by Captain Ushankov. Among them is Viktor Pritchenko, a former firefighting pilot, who discloses that the Canaries have been quarantined. Pritchenko enlists Manel’s help in scavenging for supplies, but the dark underbelly of desperation soon surfaces.
One night, he witnesses another group of refugees arrive, pleading for assistance, yet in the morning, Pritchenko dismisses their existence, leading Manel to suspect foul play as he observes the crew rifling through the refugees’ belongings. In a desperate bid for freedom, Manel reveals the location of a hospital helicopter—an escape route connected to the site of his wife’s death. Initially resistant, Pritchenko ultimately agrees to assist him.
Attempting to escape alone, Manel takes a detour through the ship, discovering two imprisoned refugees. The attempted rescue spirals into chaos when a guard shoots one of the captives. Pritchenko intervenes, killing the guard, and they hastily escape on a motorboat, though not without a casualty—the remaining refugee falls victim to the guards, and Pritchenko sustains injuries.
Upon arrival at the hospital, the elusive helicopter is missing. Manel and Pritchenko venture inside, where they encounter Lucía, a nurse, alongside a nun named Cecilia and three children who are all holed up inside. After tending to Pritchenko's injuries, Lucía reveals the whereabouts of another helicopter situated in a courtyard alarmingly overrun by zombies. Tension escalates when Ushankov's men storm the hospital searching for supplies, forcing the group to retreat through an underground boiler room.
A fierce battle erupts as zombies attack, resulting in Cecilia’s infection, who remains behind to slow their pursuers down. The others manage to reach the helicopter, but are intercepted by Ushankov’s crew. In a moment of bravery, Manel breaks open the lock to the helicopter pad, unleashing the zombies to overwhelm Ushankov. With adrenaline pumping, Manel leaps onto the helicopter, leading the group toward the Canaries, only to receive a frantic warning call from Belén, urging them to stay away. As they process the disheartening news, they witness two fighter jets streaking across the sky, signaling the outbreak's horrifying reach has now extended even to the Canaries.
