James and Letty are to be married on board ship by Captain Baines but this nearly does not happen when a group of shanghaied sailors attempt to overwhelm them, the plan being foiled by elderly Captain Jack and the marriage does go ahead. Daniel Fogarty has returned from Australia a rich man. He has begun a charity, the Albert Fund, and is knighted for his services. He marries Elizabeth at last but James's experience has prevented him from being their best man.

Having exposed Macauley's insurance scam James proposes to Letty, who accepts. Daniel also returns to Liverpool, now a very wealthy man. Robert considers opening a department store and travels with Captain Baines and Samuel to New York, where he is robbed and very nearly press-ganged. James takes on a voyage to import some sheep but it causes him to postpone the wedding and Letty, as a consequence, declares the engagement and wedding off.

Five ships, all carrying iron plate, have foundered - people betting on the losses, including Mr. Dunwoody, Elizabeth's clerk, who buys the company house where Robert and Sarah live, forcing them to return to live over the shop. James accepts a cargo of iron plate and discovers the ship is being sabotaged by Kirk, a sailor in the pay of Macauley, who also sunk the other five. Whilst Elizabeth's son, William is only interested in commerce, Robert's boy, Samuel, is keen to go to sea. James returns to Liverpool and finds that Letty, tired of waiting for a marriage proposal, has gone.

On the eve of his voyage to Montevideo Letty tells James she will marry him - in her own good time. She also gives William financial backing for his engineering schemes. Samuel meanwhile stows away on James's ship and, when caught, James sees that he is harshly treated to put him off sea-faring but the boy will not be deterred and travels on to South America, where James makes a profitable deal.

James is importing jute from Scotland and is not happy to learn that Letty's mill-workers are repairing old jute sacks, which, given that she believes in a fair wage, is under-cutting him. They argue and she is injured but, to make atonement, he takes her on his next voyage. Daniel impresses with his generosity by buying Sarah a venue for a seaman's mission but he and Elizabeth are united in their desire to stop William seeing Charlotte. They plan to send him to London but he calls their bluff.

Letty tells James she invested in William's steam engine project and he buys a flour mill in her name, sailing to Pennsylvania to buy loose grain from an ex-Cavalry officer who drives a hard bargain. James gets what he wants after a drinking bout but the grain, known as dead man's cargo, starts to shift when the ship hits a storm and needs to be moved else the ship could capsize. A man dies in the process. Daniel and Elizabeth rekindle their old flame but their decision to tell William his true parentage proves to be unwise.

James Onedin returns to Liverpool, his ships laden with grain from Turkey. The sale of this will pay off the interest on the debt and start him back on the road to solvency. As further collateral, he offers the house which he bought for Letty Gaunt and Charlotte, who will now move in with him. It is a business arrangement but Letty perhaps seeks more from him.

William makes his peace with his parents but assures them that his interest in developing steam engines supersedes his desire to inherit the shipyard. James's failure to listen to William results in the engine blowing on the ship he is using to take Polish emigrants to New York and he puts in to Liverpool for repairs. Maritsa, one of the emigrants ,is a talented lace-maker, and Robert wants to employ her in his sweat-shop but a sympathetic Samuel advises her she would be better off going on to New York. Unfortunately another accident with the steam engine leads to the ship lurching violently, trapping Maritsa's fingers in a door and requiring two to be amputated.

James and Captain Baines sail to Palermo to pick up emigrants for America. Whilst James is ashore with his Sicilian agent Benito, several Mafia bandits led by local don Ranocci take over the ship and in the subsequent gun-battle the mate is killed and Captain Baines and the crew taken hostage. They will be released if James gives Ranocci the money taken from the locals for their voyage but James has other ideas and leads the oppressed Sicilians against the Mafia. At home Letty goes into business and William is as disapproving of his parents' relationship as they are of his intense friendship with Charlotte.

Five years have elapsed. Onedin is a prisoner in a settlement in South America from where he is rescued by Captain Baines, and they return to Liverpool. Macaulay, a wealthy Australian, keen to invest in the shipping trade with South Africa, does business with the Onedin's but when the bank crashes, the Onedin's lose out as their collateral is taken. Robert loses his shop and James's ships are forfeited but he manages to get them out of port before Macaulay claims them.