In 1786: Captain William Rennie is on the beach and on half pay. Things weren't always so bad for him. So Rennie is amazed when he's given a prime commission: HMS Expedient is a 36 gun frigate; she is to be sent to the South Seas on a scientific expedition. Then a long series of mysterious accidents and setbacks occur as Expedient sails south.

Lieutenant James Hayter and Captain William Rennie are to sail to the Mediterranean, to assist Britain's ally Rashid Bey of Rabhet. Murky politics, threatened mutiny, desperate sea actions and imprisonment follow on the sweltering North African Coast, where the rules of European warfare no longer apply and the victor will take everything.

1790. Spymaster Sir Robert Greer asks retired captain William Rennie to join his former subordinate, Lieutenant James Hayter, in Portsmouth. Their mission is to intercept a contraband runner, the cutter 'Lark' and capture her captain, a disgraced Navy Lieutenant.

Though deeply disturbed by a terrible incident during his previous commission, James Hayter is nevertheless on the verge of taking command of HMS Sloop Eglantine as Master and Commander when personal tragedy shatters his life.

Spring 1792. HMS Expedient and her crew have survived their most perilous commission yet: the dead have been buried and the battle scars repaired. Captain William Rennie is anxious to be active again after a year on the beach.