Sharpe and Frederickson are arrested in Bordeaux, accused of stealing Napoleon's treasury, which has been concealed at Teste de Buch, the fortress they had captured in the previous novel. A witness statement by Napoleon's spymaster, Pierre Ducos, an old, bitter enemy of Sharpe's, reveals who is responsible for the false allegation. Sharpe and Frederickson realize that they need the testimony of the fort's French commander, Henri Lassan, to exonerate them, so with help from Harper and Captain Peter d'Alembord, the two men escape and set out to find Lassan.