Set in South Korea, the drama's first 4 episodes focus on the childhoods of Yoo Ji-ho (Ju Ji-hoon) and Yoo In-ha (Ji Chang-wook). 12-year-old Yoo Ji-ho (Kang Yi-seok) lives with his adoptive grandmother. One day, during a thunderstorm, his grandma is killed after being run over by a mysterious black car. Afterwards, Yoo Ji-ho is invited into the family of Yoo In-ha. 11-year-old Yoo In-ha (Kim Ji-hoon) is the son of a wealthy CEO of a piano company. He is an overly cocky piano prodigy, winning all of the competitions he enters. After Yoo Ji-ho is introduced as the elder son of Yoo In-ha's father, Yoo In-ha begins to feel threatened by Yoo Ji-ho, who has lots of musical talent. Chae Yeong-rang (Chae Shi-ra), Yoo In-ha's mother, is forced to accept Yoo Ji-ho as her son. She is extremely unhappy about this, especially after discovering that her husband plans to hand the company down to Yoo Ji-ho instead of Yoo In-ha. After arguing with her husband, she unintentionally strikes him down onto the ground, causing his head to bleed. Fearing that she has killed her husband, she flees, but discovers that their house is on fire. Unintentionally caused by her mother-in-law, who fell asleep after lighting the candles on a birthday cake, she rushes out of the house, begging a deaf and mute street dessert vendor to help her rescue her two grandsons. The street dessert vendor's daughter is friends with both Yoo Ji-ho and Yoo In-ha. Her name is Hong Da-mi (Kim Sung-kyung). Yoo Ji-ho taught the girl her first piano piece, while Yoo In-ha gave her official piano lessons. Realizing that her son is still upstairs, Yeong-rang rushes upstairs to rescue him from the fire. She unintentionally rescues Yoo Ji-ho instead of Yoo In-ha, believing that Yoo Ji-ho is her actual son because he is wearing the bunny pajamas that she gave to Yoo In-ha earlier. After realizing that she rescued the other son, she attempts to reenter the building, but is stopped by firefighters. Yoo In-ha sustains major injuries caused by the fire, but is thankfully saved by the street dessert vendor. Unfortunately, the man dies after a chandelier falls on top of him. Yoo In-ha discovers that his fingers are ruined due to the fire. His mother orders his doctor to perform a skin graft surgery, which would allow Yoo In-ha to play the piano once more. After the surgery, Yoo In-ha discovers that he can no longer move his pinky finger, resulting in much anguish. Yoo In-ha attempts to commit suicide by jumping off the hospital building, but is saved by his older brother, Yoo Ji-ho. After being interrogated by police about the fire, Chae Yeong-rang blames the street vendor for it, claiming that he was a thief. The street vendor's family is shamed and forced to move away. 14 years later, Yoo Ji-ho and Yoo In-ha meet Hong Da-mi (Jin Se-yeon) again, competing for her love. Who will win?
