After their state-of-the-art steamship the "Gigantic" sinks a few minutes after being launched, the MacIver brothers of Liverpool begin to plan for the future of their company. David (Griffith Jones) takes a business-like approach and eventually joins forces with former rivals, but decides the expensive gamble of steamships is not the way to go. Charles (Sir Michael Redgrave) embarks on a different course, sailing on a doomed ship to America to forge an alliance with Samuel Cunard (Hartley Power). Eventually, the brothers are reunited in their bid to gain the mail contract from the British government, although their relationship might not last since each is in love with Mary (Valerie Hobson), the daughter of one of their backers.