The Commodore: Aubrey/Maturin Series, Book 17

After a dangerous tour of duty in the Great South Sea, Jack and Stephen finally return to their families in England. For Jack, the return is joyful, but for Stephen, it is heartbreaking. His wife, Diana, has left for parts unknown; his young daughter has all the symptoms of autism. To escape these painful circumstances, Stephen joins Jack on a bizarre decoy mission to the lagoons of the Gulf of Guinea.