The world’s largest, most famous and valuable diamond, “the Allahabad” belongs to the private collection of Count Pierre Mansard, one of the wealthiest men of France. Arsene Lupin, the famed burglar who takes from the rich and gives to the poor has set his eye on the Allahabad Diamond in Count Pierre Mansard’s collection in order to gift it to his lover, Annette Lamballe. In a letter he sends to Count Pierre Mansard, he writes that he will steal the diamond in exactly two months time. Extremely distressed, the Count invites the world’s most famous detectives to Paris. Among them is also Abdülcanbaz, “the Formidable Turk” from Istanbul, whose praise he has heard about. Regardless of all these precautions, it will be difficult to stop Arsene Lupin from enacting his plan.