Following the attempted murder of Mathilde, daughter of renowned Professor Stangerson, Joseph Rouletabille, a young reporter, accompanied by photographer Sainclair, visits the Château du Glandier to try and shed some light on the mystery.

A woman is sleeping in her bedroom. Her room can not be opened from the outside, but only from inside. When suddenly one night somebody attempted to murder her. Before the police arrived the killer fled and was not to be found. The police come to investigate who the killer is and how did he get inside.—lovethebook