The drama explores whether love is a matter of the soul or the physical heart. When Min-woo and Hye-won meet by chance, her heart begins to beat uncontrollably—not just because of a new attraction, but because it "remembers" its former love.

The climax of occurs at a picturesque mountain resort. Hye-won, fleeing a sudden summer downpour, stumbles into a gazebo. Min Woo, visiting the same mountain where Soo-ah died, is standing there.

The series begins by introducing the two leads whose lives are bound by a tragic secret:

For new fans and nostalgic re-watchers alike, the quest often begins with one specific search query:

We then meet Shim Hye-won (Son Ye-jin, in her career-defining innocent role). Hye-won is a delicate florist and painter who lives in the countryside. Unbeknownst to her, she is the recipient of Soo-ah’s heart. Since the transplant, Hye-won has undergone a mysterious personality change—she is more vibrant, more emotional, and drawn to things she cannot explain (like architecture and the color blue... Min Woo’s favorites).

Years after a tragic accident takes the life of his first love, Soo-jae (played by Song Seung-heon) has become a reserved and sorrowful architect. While on a trip to a serene mountain retreat, he meets Hye-won (played by Son Ye-jin), a cheerful florist with a warm smile — but also a fragile heart condition. In a chance encounter beneath a rain-soaked pavilion, Soo-jae catches her scent, reminiscent of summer flowers and the woman he once lost. Unbeknownst to them, Hye-won is the recipient of a heart transplant — the very heart that once belonged to Soo-jae’s late love.