In 1930, on the island of Noronha in Brazil, the inmates of the penitentiary revolt. Frédéric Coulibaud, head of the aeropostale radio station, and his team-mates Mastic and Froment, try to prevent them from entering the concession where the island's governor and his daughter have taken refuge. They manage to repair the radio so as to follow and guide Mermoz as he attempts to cross the South Atlantic for the 53rd time. The aviator is forced to ditch and is picked up by a boat. Their mission accomplished, Coulibaud and his team boarded a British ship that had come to their rescue.