Some highschool students discover that underneath the school where they study, there could be some tunnels that served as a bomb shelter during the war. Nobody remembers their existence, so they decide to try and find them. They find out that some children were buried there when part of the tunnels collapsed, and one of the girls, Aixa, begins to sense a threat she can´t explain. According to some articles she finds on the Internet, the people buried there haunt the places where they died, so she considers it an “Evil School Omen”. “E.S.O”. Aixa tries to warn her friends of the danger but nobody believes her.