Clare has been in love with Henry her entire life. She believes they are destined to be together, even though she never knows when they will be separated: Henry is a time traveler--cursed with a rare genetic anomaly that causes him to live his life on a shifting timeline, skipping back and forth through his lifespan with no control. Despite the fact that Henry's travels force them apart with no warning, Clare desperately tries to build a life with her one true love.

Clare shares a deep emotional bond with Henry, a handsome librarian who travels involuntarily through time. Clare and Henry must treasure the fleeting moments they have together, knowing they can be separated without warning.