Voyager by Diana Gabaldon
In this time-travel romance, a former World War II nurse, who has returned to her life in the 20th century, discovers that her 18th-century Scottish lover may still be alive. Driven by hope and longing, she embarks on a perilous journey through the standing stones of Scotland to reunite with him. Their passionate reunion is shadowed by the political unrest of the era and the personal vendettas that threaten to tear them apart once again. As they navigate the dangers of the past, they must confront the consequences of their time apart and the changes it has wrought in them both.