What is the main conflict in Hornblower and the Atropos by C.S. Forester?

The novel presents a series of episodes in the life of Horatio Hornblower, the protagonist and dominant character. The narrative begins with Hornblower, his pregnant wife Maria, and their infant son taking passage aboard a canal boat traveling from Gloucester to London. Early in the voyage one of the canal boat's two crewmen is incapacitated, and Hornblower volunteers to steer the boat. Maria is distressed that her husband deigns to manual labor, but Hornblower finds the canal boat's operation fascinating. Additionally, he wants to get to London as quickly as possible to take up his new appointment as captain of HMS Atropos. After an interesting voyage, Hornblower arrives in London, sees Maria to a hotel, and assumes command of his ship.