Marc has been trapped inside his Barcelona office for three months. Outside, the world has plunged into chaos following the outbreak of a fatal type agoraphobia known as the Panic, which kills anyone who ventures outdoors. Desperate to tunnel out in order to try to find his girlfriend, Marc makes a tense alliance with Enrique, a coworker who has a rare, functioning GPS. Equipped with only minimal supplies and a desperate need to escape, the two embark on a journey through the lawless, hostile subway tunnels and sewers in search of their loved ones.