Captain Jack Aubrey is ashore on half-pay without a command until his friend, surgeon and secret agent Stephen Maturin arrives with secret orders for Aubrey to take a frigate to the Cape of Good Hope, under a commodore's pennant. But the difficulties of carrying out his orders are compounded by two of his own captains - one a pleasure-seeking dilettante, the other liable to provoke the crew to mutiny. Based on the actual campaign of 1810 in the Indian Ocean.