It is six months since the death of his wife Anne and James is still mourning her loss. Gradually he considers a second marriage and finds himself having to choose between two women: the adoring eighteen year old Leonora Biddulph, daughter of a wealthy coal merchant and Caroline Maudsley, in her late twenties, a sophisticated wealthy widow whom he rescues from a dugout canoe on the Amazon River.
There are many new opportunities for James Onedin and his shipping line. The newly built Brazilian State Railway opens up a promising source of trade with constant demand for coal and iron. James is determined to win the contract but Frazer also has plans involving the use of Fogarty and a steamship. Later, Fogarty gets the better over James when he is successful in smuggling rubber seeds, black gold out of Brazil for the development of plantations in India. Working the Onedin ships hard for every dollar, James journeys to the Baltic, East Africa, America and north-east Canada.
Extensive location filming is again a feature of The Onedin Line and highlights in Series Three include a spectacular storm filmed in the Baltic Sea.