Captain Jack Aubrey a brilliant and experienced officer has been struck off the list of post-captains for a crime he did not commit. His old friend Stephen Maturin usually cast as a ship's surgeon to mask his discreet activities on behalf of British Intelligence has bought for Aubrey his former ship the Surprise to command as a privateer more politely termed a letter of marque. Together they sail on a desperate mission against the French which if successful may redeem Aubrey from the private hell of his disgrace.