New York, 1850. Two clipper ships depart on a race around Cape Horn to the boomtown of San Francisco, where the first to arrive will gain the largest profits and also win a $50,000 wager for her owner.

Sapphire is a veteran ship with an experienced crew. Achilles is a new-build with a crimped, mostly unwilling crew. Inside Achilles' forecastle space reside an unruly gang of British sailors whose only goal is to reach the gold fields, a group of contrarily reluctant Swedish immigrants whose only desire is to return to New York and the luckless Englishman, Harry Jenkins, who has somehow managed to get himself crimped by the equally as deceitful Sarah Doyle, and must now spend the entire voyage working as a common sailor down in Achilles' forecastle while Sarah enjoys all the rich comforts of the aft passenger saloon.

Despite having such a clear advantage, Sapphire's owner has also placed a saboteur, Gideon, aboard Achilles with instructions to impede her in any way possible. Gideon sets to with enthusiasm and before she even reaches Cape Horn Achilles' chief mate and captain have both been murdered. Her inexperienced 2nd Mate, Nate Cooper, suddenly finds himself in command of Achilles and, with the help of the late captain's niece, Emma, who herself is the only experienced navigator remaining on board, they must somehow regain control over this diverse crew of misfits and encourage them onwards and around the Horn.

But it is the ladies on board Achilles who finally regain control of the situation. With the help of their passenger complement, which includes a French Madam and her three girls, Emma and Sarah do all they can to manipulate this crew as they in turn confront sea, weather, a murdering saboteur and one another and struggle to reach their destination ahead of Sapphire.