It is February 1818, and Adam Bolitho longs for marriage and a safe personal harbour. But with so much of Britain's fleet redundant, he knows he is fortunate to be offered H.M.S. Onward, a new 38-gun frigate whose first mission is not war but diplomacy, as consort to the French frigate Nautilus.

Under the burning sun of North Africa, Bolitho is keenly aware of the envy and ambition among his officers, the troubled, restless spirits of his midshipmen, and the old enemy's proximity. It is only when Nautilus becomes a sacrificial offering on the altar of empire that every man discovers the brotherhood of the sea is more powerful than the bitter memories of an ocean of blood and decades of war.