Shortly before the war, strange things happen at night at the School of Saint-Agil. Students begin to disappear... Three students of Saint-Agil, Beaume Sorgue and Macroy, have created a secret society to prepare leaving for America. One evening, one of them, Sorgue, sees a man through a wall in the natural sciences class. He then disappears after having been sent to the principal's office. When Macroy vanishes in turn, the whole institution is in turmoil. The last member of the secret society still at school, Beaume, might be expelled as well after the yearly school party. During this party, Lemel, the alcoholic art teacher, dies after a fall when a power outage leaves the school in the black. Everyone believes in an accident but Beaume decides to investigate. He chooses to disappear as well and, with the help of the mysterious and spooky English teacher, he manages to discover the counterfeiting business at work in the school insides.