Gaston Leroux is best known for writing the novel The Phantom of the
Opera. However, he also wrote some excellent detective stories. In
fact, Leroux's contribution to French detective fiction is considered a
parallel to Sir Arthur Conan Doyle's in the United Kingdom and Edgar
Allan Poe's in America. In this, his most popular mystery, rival
detectives try to crack the following case: Madamoiselle Stangerson
retires to bed in the Yellow Room. Suddenly, revolver shots echo through
the house and she screams for help. Her father and a servant run to the
locked room where they find the wounded girl - alone. The only other
exit, a window, is barred. How had the assailant escaped?