At the Château de Thibermesnil on the Normandy coast, a boastful banker entertains his dinner guests with two prized secrets: a centuries-old hidden passage no one has ever been able to find, and a great hall packed with the treasures his family gathered over hundreds of years. Among the guests is a charming marine painter named Horace Velmont, who listens with rather more interest than the others. For Velmont is not at all what he appears to be. That night the treasures vanish through a passage that should not exist. And the very next afternoon, the one man who might unravel it steps off the train from England: Sherlock Holmes himself. But the great detective has come a day too late, straight into a duel of wits with the most gracious thief in France — Arsène Lupin, who is always one move ahead, and far too well-mannered to gloat. This is the legendary first meeting of Arsène Lupin and Sherlock Holmes: the closing story of Maurice Leblanc's collection, which set France's gentleman burglar against England's greatest detective and delighted readers on both sides of the Channel.