Yoo Min-Woo's (Song Seung-heon) first love was Seo Eun-Hye (Shin Ae). However, Eun-Hye gets into a car accident and dies. Without Yoo Min-Woo's knowledge, her parents decide to donate her organs. Shim Hye-Weon, (Son Ye-jin) has suffered from a fatal heart disease ever since childhood. Miraculously, she finds that she will be obtaining a heart from a donor, the deceased Seo Eun-Hye.
Suffering from the pain of losing Eun-Hye in an accident, Min-Woo goes to Italy to study, with the memories of Eun-Hye still lingering in his heart. When he returns to Korea, fate takes a turn and brings Hye-Weon and Min-Woo together. When the two first meet at the airport, Hye-Weon's heart (Eun-Hye's heart), oddly beats faster when she is around Min-Woo.
Park Jeong-Jae (Ryu Jin) is Hye-Weon's fiancee. Jeong-Jae's sister, Park Jeong-Ah (Han Ji Hye) meets Min-Woo in Italy and falls for him. Hye-Weon doesn't know why or what she feels when she's with Min-Woo. Min-Woo feels guilt towards Eun-Hye, because his feeling of love are stirred once again as he keeps being around Hye-Weon.
Through coincidence, Min-Woo ends up being hired as the Art Director for Jeong-Jae's project "Summer Scent" and Hye-Weon as their florist. Hiding their prior encounter in the forest, they awkwardly greet each other as if they'd never met. During the project, their fondness deepens, and Min-Woo begins to 'recognise' similarities between Eun-Hye and Hye-Weon. Hye-Weon, on the other hand, believes it to be fate that her heart beats faster whenever Min-Woo is near. Their fondness for each other soon triggers Jeong-Ah's and shortly thereafter, Jeong-Jae's suspicions. Jeong-Jae, however, chooses to turn a blind eye as he deeply loves Hye-Weon. It is then Hye-Weon's turn to be confused as to whether her feelings for Min-Woo are true, and as a result, decides to leave Min-Woo, trying to cover up her feelings of guilt towards Jeong-Jae and Jeong-Ah. She returns to Jeong-Jae's side.
To forget Hye-Weon, Min-Woo decides to leave for Italy indefinitely but only after seeing her one last time. At her wedding, Min-Woo casts one last glance at her and then leaves. With Min-Woo near, Hye-Weon's heart once more signals his presence, and just as soon alerted, she sees Min-Woo leaving. Desperately trying to catch Min-Woo, Hye-Weon collapses. Min-Woo rushes Hye-Weon to the hospital with Jeong-Jae arriving a little later. Jeong-Jae, angry at Min-Woo for having caused Hye-Won's collapse, tells him to leave for Italy but Min-Woo agrees to leave only after Hye-Weon has regained consciousness. Soon, Hye-Weon wakes up and a deeply angered Jeong-Jae forbids Min-Woo to meet, ordering him to leave on the spot. However, Min-Woo agrees to leave only after Hye-Weon promises him to to have heart surgery for not going through with the operation would mean her certain demise.
Soon after his arrival in Italy, Min-Woo receives a letter notifying him that Hye-Weon has died during the operation.
3 years later, with memories of Hye-Weon in his heart, Min-Woo returns to Korea as a manager of an Art Centre. During his absence, Hye-Weon has undergone an heart transplant after the initial surgery, and then traveled to the United States for another transplant. On his way up the steps at the Art Centre and on her way down after her delivery, they meet again. This time with her new heart, yet, its abnormal beating confirms Min-Woo's presence to Hye-Won and thus once and for all, confirms their love for each other to be authentic.