Dans la clairière derrière sa maison, Clare Abshire, six ans, rencontre pour la première fois Henry DeTamble, un voyageur temporel de 36 ans. Quatorze ans plus tard, une réunion inattendue à la bibliothèque donne à Henry l'occasion de rencontrer Clare.

After a rocky "first" meeting, Henry and Clare attempt to reset with a second date, but she still struggles to rectify this version of Henry with the man she's known – and loved – all her life. To help her better understand the difference between this 28-year-old and the man she'll help him become, Henry takes Clare back to the most formative moment of his childhood.

After meeting her soulmate at age six, Clare laments a linear lifetime defined by waiting for Henry’s unpredictable appearances. Meanwhile, an incident at a high school party finds a distraught teenage Clare turning to Henry for help.

Clare hosts a couples’ dinner party to introduce Henry to her roommate Charisse and best friend Gomez, but when it’s crashed by another Henry and his girlfriend Ingrid, deeply held secrets are revealed. Meanwhile, Clare remains determined to make her 18th birthday — and fated 152nd meeting with Henry in the clearing — unforgettable.

Despite all the years spent together in the clearing, Henry makes a complicated trip to Clare’s childhood home for the first time.