The Head of Caesar

In G.K. Chesterton's "The Head of Caesar" from the Father Brown series, a young woman named Christabel Carstairs, the daughter of a renowned coin collector, approaches Father Brown after being blackmailed by a mysterious man with a crooked nose, who threatens to expose her theft of a valuable Roman coin from her late father's collection, a coin with the likeness of Caesar that she impulsively took because it reminded her of a young man she was infatuated with; Father Brown, through his keen observation skills, uncovers the truth behind the blackmail and the identity of the culprit, who is revealed to be someone close to the family with a hidden motive related to the inheritance of the coin collection.