The first four books in the Outlander series by Diana Gabaldon—Outlander, Dragonfly in Amber, Voyager, and Drums of Autumn—follow a World War II nurse who is mysteriously transported back to the 18th century, where she becomes deeply involved in the lives, conflicts, and historical events of the time; as the story unfolds across Scotland, Europe, and colonial America, it explores her relationships, separations and reunions, and the challenge of building a life across different eras, blending time travel with historical adventure, romance, and themes of loyalty, survival, and identity.