The concepts of roads not taken and domino effects have received plenty of cinematic attention in their showier forms by way of multiverse comic book movies and dimension-hopping films like Everything Everywhere All At Once. But, though there’s no hint of sci-fi in Past Lives, Celine Song’s gentle film can count itself as one of the best treatments of that universe-spawning question: “what if?”

When her family moves from Seoul to Canada, teenage Na Young bids a loaded farewell to classmate Hae Sung and changes her name to Nora. Years later, they reconnect online and discover the spark still burns between them. This is no idealistic romance, though: Past Lives is told with sober candor. Song acknowledges real obstacles standing in the way of a relationship between the two — those pragmatic (distance) and, more painfully, personal (evolving personalities, American husbands).

Those two threads — unrealized romance and the transmutation of identity that so often takes place after migrating — are expertly entwined in Past Lives to produce a sublime, aching meditation on memory and time, practical love and idealistic romance, and all the complex contradictions that exist in between. That Song communicates so much and so delicately in only her first film makes Past Lives all the more stunning.

The film’s empathetic balancing act. Twenty-four years after leaving Seoul, Nora (Greta Lee) finds herself married to fellow author Arthur (John Magaro). Twelve years after they reconnected, Hae Sung (Teo Yoo) is on his way to New York to see Nora for the first time. Both have nebulous expectations and intentions for their reunion: they know there’s something to be worked out between them, but it’s not something easily named. Someone else who knows that is Arthur, who could so easily be the villain standing in the way of Nora and Hae Sung realizing their true destiny. As Song writes him and Magaro plays him, though, he’s not: while he’s palpably nervous about what Hae Sung means to Nora, he doesn’t move to interfere in what needs to happen between them. Lee and Yoo’s performances are similarly fully realized, giving Past Lives all the aching complexity and profundity of real life.