Disguised as a maid, Lady Penelope Lytton sails to America to escape her abusive guardian with secret plans to meet and marry her childhood sweetheart in order to regain her inheritance.

US marshall Parker Davis is a self-made man who toiled as a boy in the coal mines after losing his father to those same mines. He disdains those with power and wealth, like aristocrats, who suck the life out of laborers for profit. As a special agent for President Grant, his life now revolves around ferretting out secrets. Determined to uncover Penny's, Parker decides she needs his protection. He offers marriage, but to Penny, Parker is as controlling as her guardian and no better a choice for a husband. She's intent on keeping her plans.

After discovering Penny is a noblewoman who owns one of the biggest coal mines in England, Parker believes she's snubbed his offer because he's common. Despite the temptation Penny stirs, Parker wants nothing to more do with her.

As they work their way toward happily-ever-after, Penny's guardian tracks her to America. He's not about to leave his heiress behind, even if it means killing Parker to achieve his goal.