Captain Jack Aubrey is ashore on half pay without a command - until Stephen Maturin arrives with secret orders for Aubrey to take a frigate to the Cape of Good Hope under a commodore's pennant, there to mount an expedition against the French-held islands of Mauritius and La REunion. But the difficulties of carrying out his orders are compounded by two of his own captains - Lord Clonfert, a pleasure-seeking dilettante, and Captain Corbett, whose severity pushes his crew to the verge of mutiny.