A brave captain pilots the first steamboat line between England and the U.S.

In Liverpool, England, in 1837, young brothers Charles and David MacIver, who have inherited a banking and shipbuilding firm from their father, attend the launching of their first steamship, which is intended for use in the British coastal trade. After the mayoress christens the vessel The Gigantic , it sets off down the slipway and promptly sinks. Business rival Josiah Eagles, who operates sailing ships that take emigrants to America, celebrates the disaster. Charles tries to convince David that they must persevere with their plans for steamships, but David refuses, fearing further financial loss. Charles then tells David that he will continue alone and intends to go to Nova Scotia to consult with Samuel Cunard, who operates mail ships between America and Canada. Charles surrenders all his interest in the firm to David and, incognito, books passage on one of Eagles' emigrant sailing ships, the Anne of Liverpool . Eagles is an unscrupulous operator and crams too many people and too much cargo onto the ship, which has a mostly shanghaied, inexperienced crew. Fifty-five days out of Liverpool, the ship encounters a violent storm. Below, in the oppressively crowded deck, the emigrants, many of whom are sick, have exhausted their rations and have no water. Several start a mutiny, and a child dies, despite Charles' efforts. The storm rages on, and the ship sinks. Meanwhile, at his firm's Glasgow office, David tries to save the business and goes to see an old family friend, financier Donaldson. There, he meets Mary Morison, Donaldson's niece, whose father James is Her Majesty's Customs Controller for the port of Glasgow. David asks Donaldson to invest £20,000, but he declines to help. Later, when David is in the process of closing down the Glasgow office and paying off the staff, another rival, George Burns, proposes an amalgamation of their companies, and David readily agrees to the plan. At Lloyd's of London, after checking on the insurance claim on the Anne of Liverpool , Eagles learns that a Canadian ship is arriving with survivors of the disaster. Charles, who is one of the few survivors, attacks Eagles, and becomes further enraged when he learns that David has joined Burns. Later, after the Admiralty invites bids for a steam mail service across the Atlantic, Charles tries to interest several bankers in the venture without success until he happens to meet Cunard, who is in Britain attempting to acquire the mail route. Cunard suggests that they work together, and the Admiralty eventually awards the contract to Cunard, who must then find the funding to finance it. When Charles calls on Donaldson, he is unaware that David, who is about to become engaged to Mary, is attending a party there. Charles meets Mary first and enthusiastically explains to her that he and Cunard have hired famous engineer Robert Napier, and that they want her uncle to back their company. Mary then brings the estranged brothers together again, but David informs Charles that Donaldson is only interested in his company. When Cunard and Napier arrive, however, Mary argues on their behalf, as she believes in the future of steamships. Cunard then suggests that all parties collaborate in the new venture and an agreement is reached. They lay the keel of their first ship, The Britannia , although their plan for a fleet of steamships causes some labor unrest in the shipbuilding trade. Mary finds her affections shifting from David to Charles and tells Charles that she is going to America for a year to stay with her aunt in Vermont. As her father does not approve of steamships, Mary is to sail on Eagles' sailing ship, Queen Mary . The sailing ship is scheduled to leave at the same time as The Britannia in its maiden voyage, and a race between steam and sail is initiated. Just before departure, the rival crews trade insults, and while Mary transfers to The Britannia a brawl erupts. Eventually, both ships leave port. In a heavy storm, The Britannia experiences engine trouble and, even though it hoists a sail, is in danger of capsizing. Mary goes to Charles and they profess their love for each other. When a piece of wood becomes jammed in the starboard paddle box, causing the paddle to stop and the ship to list dangerously, Charles successfully frees it and saves the ship. The Britannia reaches Boston in the record time of two weeks and receives a great welcome. With its triumphant return voyage, the future of steamships is assured.