Hornblower is assigned to escort a duchess back to England on a Spanish ship he captured. He is also assigned to take top secret papers back with him. On the trip, the ship runs into a deep fog and suddenly the crew finds themselves in the middle of the Spanish Armada and taken prisoner. The papers are hidden in the duchess' undergarments for protection. But Hornblower doubts his decision to do this when he finds that the duchess speaks Spanish, is given free reign of their island, and that she is not a real duchess - but rather is an actress. Hornblower's men also start doubting him as he becomes attracted to the duchess and is given freedoms and food not offered to the others.