Three years ago, Liu Minyu (Song Seung-heon) lost his beloved fiancée unexpectedly. He chose to study abroad with a sad heart. At that time, Shen Huiyuan (Son Ye-jin) was a quiet girl with congenital heart disease. She could only sit in the corner while watching others jumping healthily. Three years later, Huiyuan, who had previously undergone a heart transplant, became lively and cheerful, and also had a beloved boyfriend. At the airport, Huiyuan passed by Minyu who had returned from abroad and felt the rapid beating of her heart. After returning to China, Minyu went to the mountain where he had climbed with his fiancée, and met Huiyuan who was lost there. The two were trapped in the mountain and had communication. Huiyuan felt the rapid beating of her heart again, and Minyu saw the shadow of his deceased fiancée in Huiyuan. In order to thank the family who donated her heart, Huiyuan ran around looking for clues, and at her destination she met Minyu who was visiting his fiancée's family. It turned out that the two were connected in this way...