In a cafe in Madrid; two random people are shot dead by an unknown sniper when they leave the bar. The streets are evacuated, and gradually, the rest of the peoplestill alive in the bar come to realise someone in the group is the reason. It becomes clear that it is a government op and they are covering up the killings under the guise of a fire. Everyone inside the cafe turns against each other. Eventually, a man emerges from the bathroom in a critically diseased condition. He drops to the floor but as the group gather around to comfort him, he mutters, "Don't touch me!" before dying. It now becomes clear that the group are being quarantined due to the man's disease. Amparo, the shop owner acknowledges the man's last words before dying and keeps five people from the group at bay who made physical contact with the man, including Elena, Nacho, Trini, Sátur and Israel believing them to be infected. Two others who believe to have made no physical contact with the man including Andrés and Sergio join Amparo and together lock the five people down in the cellar. Deep down in the cellar, the group hear gunshots coming upstairs from the bar and deduce the government have stormed in and shot Amparo, Andrés and Sergio dead. The government then burn the bar down to disinfect it. The group wait till the government is gone and head upstairs to find the interior of the bar burnt down and taped up from the outside. Eventually, the group deduce that the man has brought in what they conclude to be four doses of vaccine made for the man's disease that have supposedly infected the group. Israel finds the vaccines in the bathroom, but when the rest of the group urge Israel to share them, he reminds them that the four vaccines are not enough for the five of them, meaning someone in the group is in danger. Unwilling to take any chances, Israel deliberately takes out one of the doses and injects himself with it. Furious, Sátur engages in a physical fight with Israel. In the ensuing fight, the rest of the vaccines end up falling through a drainpipe in the cellar that leads down to the sewers. The whole group barely manage to squeeze through the small drainpipe to access the sewers. Once down, the group are still left with the question on who is going be left out to be vaccinated. Trini kills herself to minimize the group's quantity with that of the vaccines. Meanwhile, a now demented Israel kills Satur out of spite and chases after Elena and Nacho through the sewers. The two find a ladder to escape from the sewers. As they start climbing it, Israel catches up and grabs hold of Nacho. Nacho sacrifices himself for Elena by dropping himself down with Israel, resulting in both being killed. Distraught, Elena injects herself with the vaccine before climbing out of the sewers and into the streets, where she sees the bar burnt down from the outside. Nevertheless, she walks away from the scene and into the crowd.
