In the early 1970s, Henry DeTamble faces a tragic car accident that claims the life of his mother, Annette DeTamble. However, in a twist of fate, he survives by unintentionally traveling back in time two weeks. Shortly after, he encounters an older version of himself, also displaced in time. As Henry grapples with the uncontrollable nature of his time travel, he finds himself revisiting pivotal moments and relationships in his life, yet he is powerless to alter the course of events, aside from minor changes brought about by his presence.
Fast forward to 1991, where Henry finds himself in a library, where he meets Clare Abshire for the first time, much to her elation. Clare shares her extraordinary history with Henry, revealing that she encountered his future self as a child, who foretold their eventual meeting. Over the years, Clare developed feelings for Henry, only to be disheartened upon discovering his marriage. On her 18th birthday, two years prior to their library encounter, older Henry kisses her, leading Clare to realize that this man will be her husband in the future. As they embark on a romantic relationship, they must navigate the challenges posed by Henry's unique time-traveling disorder.
Henry's unpredictable journeys complicate matters further, as he often arrives at various points in time completely naked. He becomes adept at picking locks and "borrowing" clothes to manage his travels. His escapades frequently include visits to a young Clare, from whom he acquires information about when to find her waiting with garments. Despite the hurdles, Clare eventually marries Henry. However, during the wedding, he time-travels away, leaving an older version of himself to step in at the ceremony.
As Henry's time-traveling episodes escalate, they strain his relationship with Clare. In a bid to remedy their problems, he buys a winning lottery ticket using the numbers he foresaw. Yet, the underlying issues remain. Their relationship is further shaken when they witness a wounded, middle-aged version of Henry momentarily appear, raising fears about his lifespan. Having a child presents additional complications, as Henry’s genes lead to their unborn children experiencing time travel, resulting in numerous heartbreaking miscarriages. In a desperate attempt to ease their pain, he undergoes a vasectomy in secret. Nevertheless, Clare surprises him by becoming pregnant one final time—thanks to a younger version of Henry visiting—and she successfully carries the baby to term.
Before the child’s birth, Henry jumps forward in time, delighted to meet their pre-teen daughter, Alba, who reveals she is also a time traveler with a greater grasp of her abilities. In a poignant moment, Alba shares the heartbreaking news that Henry will die when she is just five years old, a truth he chooses to keep from Clare.
In the years that follow, Alba’s older self frequently visits her past self, guiding her through the understanding of Henry's fate. During one devastating birthday celebration, Clare learns of Henry's impending demise. Later on, following a severe time travel mishap that leaves him injured, Henry makes another jump, only to be accidentally shot by Clare’s father while hunting. He manages to return in time to spend his final moments in Clare's embrace. Years later, a younger Henry appears to Alba and Clare, sparking hope in Clare that he may return once more. Yet, he urges her not to wait for him, hoping this encounter grants closure for both Clare and Alba, allowing them to cherish the moments they had together.
