Dark Lightning (Part One of Three) by Mary L. Farmer

Haven Meadows has put the last two painful years behind her: she’s starting classes at Philadelphia University, making new friends, and earning good money working for her brother’s auction company on the weekends.

Her future looks bright again until she uncovers a strange old chest tucked away in an old barn. Even more bizarre is the reaction of the farm’s elderly owner to this news, who tearfully begs Haven to perform an unusual favor. She reluctantly accepts the task, and the next thing Haven knows she’s been catapulted back in time to October of 1776.

Bewildered and frightened by her extraordinary predicament, Haven tries to blend in with colonial society while she conducts a desperate search for the old chest–the only thing she believes can take her back to the present. But there’s another time traveler searching for it as well: Jean-Claude Faucheur will stop at nothing to acquire the chest and use its mysterious capabilities for his own gain. And once he lays his dark eyes upon Haven, he decides he wants to possess her too.