Professor Stangerson's daughter Mathilde is attacked and almost killed in her room, which was locked and bolted from the inside at the time of the attempted murder. Footprints lead out of one of the windows in the pavilion, but the shutters were closed and all the other windows of the building are barred. How did the attacker enter and leave the hermetically sealed room without being noticed by the professor and his servant? It's up to journalist and amateur detective Joseph Rouletabille to solve this classic in detective fiction.
