Napoleon has been defeated at Waterloo, but the ensuing peace becomes ugly for Captain Jack Aubrey, with violent celebrations of the English sailors in Gibraltar and the desertion of nearly half his crew. To cap it all off, the Surprise is nearly sunk one night in a shattering collision on the first leg of her journey to South America, where Jack and his friend Stephen Maturin are to help Chile assert her independence from Spain.

The delay for repairs reaps a harvest of strange consequences, and the South American expedition is a desperate affair, starting with near disaster in the ice-choked seas far south of the Horn. In the end, Jack, again the daring frigate commander of old, stakes all on a desperate solo night raid against the might of the Spanish viceroy in Peru. Jack's bold initiative to strike at the vastly superior Spanish fleet precipitates a spectacular naval action that will determine both Chile's fate and his own.