In 1968, a Polish girl looks up at the winter stars, while in France, another girl admires the first spring leaf. Fast forward to 1990, a young Polish woman named Weronika is performing with her choir at an outdoor concert when a sudden rainstorm disrupts their show. That night, after sharing an intimate moment with her boyfriend, Antek, she prepares to leave for Kraków the following day to visit her ailing aunt. Weronika confides to her father about a peculiar sensation, feeling as though she is not alone in the world. Upon arriving in Kraków, she joins a local choir and secures her spot with a successful audition.
One fateful day in the Main Square, while strolling about, Weronika encounters a French tourist who bears an uncanny resemblance to her. She watches in awe as her doppelgänger boards a bus, snapping photographs. However, during a subsequent concert where she performs a solo, misfortune strikes as Weronika suffers a cardiac arrest and tragically dies.
On the very same day in Clermont-Ferrand, France, Véronique, her French counterpart, is engulfed in sorrow following her intimate encounter with her boyfriend. She soon informs her music teacher of her decision to leave the choir. In school, she takes her class to a marionette show, and later, she leads them in a piece by the 18th-century composer Van den Budenmayer, whose music Weronika had sung before her untimely demise. That evening, Véronique encounters a puppeteer at a traffic signal, who gestures for her to not light her cigarette incorrectly. Soon afterward, she receives a mysterious phone call featuring a choir performing Van den Budenmayer’s composition.
Véronique's journey continues as she discovers a package containing a shoelace. This leads her to learn more about the puppeteer, Alexandre Fabbri, a children's book author whose work captivates her. Following this, she receives a curious package from her father, featuring a cassette tape with various sounds, including a typewriter and fragments of Van den Budenmayer's music. The postage stamp guides her to the Gare Saint-Lazare in Paris, where she meets Alexandre at a café. He admits to sending the packages as a means of drawing her to him. Initially angry, Véronique checks into a nearby hotel, but Alexandre soon follows, apologizing. They express their feelings and drift into a peaceful sleep together.
The next morning, Véronique opens up to Alexandre, revealing that throughout her life, she has felt as though she exists “in two places at the same time,” sensing that a guiding presence has influenced her path. She shares insights from her handbag, including a proof sheet from her trip to Poland. Alexandre spots what appears to be her image in a photo, but she insists it isn’t her. Sensing the weight of their connection, Véronique breaks down in tears while Alexandre provides comfort, realizing that Weronika’s destiny has profoundly affected Véronique's choice to step back from her singing pursuits.
As we delve deeper into their intertwined lives, Véronique visits Alexandre at his apartment, witnessing him create marionettes that echo her likeness. He articulates his need for a backup puppet should the original break. He demonstrates the puppet's operation while the duplicate remains inactive on the table. Later, he shares with her his new book—the tale of two women born on the same day in distinct cities with a mysterious bond. That same day, Véronique visits her father’s home and caresses an ancient tree trunk, prompting her father inside to feel her presence, hinting at the connection that transcends their shared existence.