When she finds a ring in his office with the Scarlet Pimpernel symbol.
Explanation:
"The Scarlet Pimpernel" is a book written by Baroness Orcz that tells the story of Percy Blakeney, a nobleman who, during the French revolution, disguised himself as the hero Scarlet Pimpernel, to save other nobles who were condemned to be killed in the guillotine. The hero develops many enemies because of this activity and is pursued by many who wish to discover his identity. One day Blakeney's wife, Marguerite finds a ring in her husband's office. This ring was very well kept and features the symbol of Scarlet Pimpernel, making her discover that her husband and hero are the same person.
