Let's take "Outlander" by Diana Gabaldon.
In 1945 Scotland, former World War II nurse Claire Randall is enjoying a second honeymoon with her husband, Frank, when she stumbles upon ancient standing stones on the hill of Craigh na Dun. Upon touching them, she's mysteriously transported back in time to 1743. In this unfamiliar and dangerous world, Claire is immediately caught up in the Jacobite uprisings and the harsh realities of 18th-century Highland life.
To survive, she's forced to marry Jamie Fraser, a young, rugged Scottish warrior with a kind heart and a fierce loyalty. Their marriage, initially a means of protection, blossoms into a passionate and deep love that transcends time itself. Jamie's bravery, humor, and unwavering devotion captivate Claire, while her intelligence and modern medical knowledge make her invaluable to the clan. They face numerous challenges, including political intrigue, violent conflicts, and the constant threat of Claire's secret being discovered.
As Claire and Jamie's love deepens, they build a life together in the Highlands, filled with both joy and hardship. However, the shadow of Claire's original time and the looming Battle of Culloden threaten to tear them apart. Claire must make a heartbreaking choice: stay in the past with the man she loves or return to her own time, leaving Jamie behind forever. Their story is a sweeping epic of love, adventure, and the enduring power of the human heart across centuries.