When the bomb hits, teacher Paul becomes a leader within his school. He ensures a handful of students are able to survive the blast and brings them the only place he believes they'll be safe from the radiation - an abandoned system of mines. Plunging into the darkness of abandoned canals and mine shafts, Paul quietly grieves his girlfriend, Anya, who is surely dead from the blast. He forces his sadness aside and discovers a secret cavern where he and the surviving students will be safe. A brief sexual relationship with his coworker, Jean, provides solace. However, it's short-lived - insanity dwells in the tunnels leading from the cavern, nicknamed "the narrows." First Paul hallucinates, then some of the boys go missing, the survivor claiming to have stumbled across creatures living in houses in another cavern. With the radiation seeping into their new home, Paul reluctantly leads the children into the narrows. The group quickly crumbles as, one by one, they go mad and flee from one another. Finally, Paul is alone. He walks until he stumbles upon a vision of his lost girlfriend, Anya. He attempts to run from her, hoping death will claim him before she does, but cannot escape her ghost.