The Fortune of War - Patrick O'Brian

Captain Jack Aubrey arrives in the Dutch East Indies to find himself appointed to the command of the Fastest and best-armed frigate in the Navy.

He and his friend, the surgeon and secret agent Stephen Maturin, take passage to England in a despatch vessel. But the War of 1812 breaks out while they are en route. Bloody actions precipitate them both into new and unexpected scenes where Stephen’s past activities as a secret agent retur on him with a vengeance