Laura Elizabeth Woodbury, heir to a Montana cattle ranch, has just lost her father. A year ago, he bestowed upon her the nickname, "princess Sapphire" when he discovered sapphires in a mine where, sixteen years earlier, he'd found gold. The independent Laura is astonished to learn her father has hired a fancily-dressed stranger to assist her in finding a suitable husband, and to help run the ranch.

Matt Black is the right hand man of a Minnesota railroad baron who'd been a friend of Laura's father. Matt's been hired to head up a team of railroad workers replacing damaged railroad tracks across Montana and to find a decent man to marry Laura. Matt is completely unprepared for the headstrong, willful blond and soon finds himself in love with her. Laura feels the same way about Matt—until she learns his secret that will change her life completely.