Tessa Taylor arrives in 1870s Upper Peninsula, Michigan, planning to serve as a new teacher to the town. Much to her dismay, however, she immediately learns that there was a mistake, that the town had requested a male teacher. Percival Updegraff, superintendent and chief mine clerk, says she can stay through winter since they won't be able to locate a new teacher before then, and Tessa can't help but say she is in his debt. Little does she know that Percival will indeed keep track of all that she owes him.
Determined to become indispensable, Tessa throws herself into teaching, and soon the children of the widowed lighthouse keeper have decided she's the right match for their grieving father. Their uncle and assistant light keeper, Alex Bjorklund, has his own feelings for Tessa. As the two brothers begin competing for her hand, Tessa increasingly feels that someone is tracking her every move, and she may not be able to escape the trap that has been laid for her.
