In 1814, Sara Stevenson, the well-bred but high-spirited daughter of celebrated Scottish lighthouse designer Robert Stevenson, falls in love with a common sailor, Thomas Crichton. On the day of their clandestine elopement, Thomas mysteriously disappears, leaving Sara heartbroken, secretly pregnant, and at the mercy of her overbearing family. Refusing to relinquish her hopes that Thomas will someday return to her, Sara is banished to an eerie lighthouse on lonely and remote Cape Wrath. There she meets William Campbell, the reclusive yet dashing light-keeper who incites her ire - and interest. Soon Sara begins to accept her life on the cape and her growing attraction to William - until a mystifying package from an Oxford antiquarian arrives, giving intriguing clues to Thomas's whereabouts. Through her correspondence with the antiquarian, Sara slowly uncovers the story of her beloved's fate. But what she doesn't immediately grasp is that these letters travel an even greater distance than she could have imagined - as the boundaries between time and space unravel to forge an incredible connection between a woman and a man many years apart.