The play is based upon a story written by Sardou and first published in December 1861 under the title The Medallion.
Sara Vanderven arrives, and Cornelius informs her that Balthazar has been in love with her for years, but is too intimidated to let her know.
Sara agrees to marry Balthazar, if he will bring to her home a certain locket, which contains a flower that had meant something to them when they were children.
Help soon arrives in the form of Burgomaster Tricamp, a rather Sherlockian detective who quickly determines that the crime was perpetrated by a small woman, who is not an experienced thief and knows the house intimately.
Reexamining the physical evidence of the crime, Cornelius declares that he knows who the criminal is, and that it is not Christiane but in fact a bolt of lightning.