An unexpected phone call summons an elderly woman, who has lost interest in life, back to Korea and the remote cottage in the countryside where she spent a tumultuous time in her youth. Memories overwhelm Suni (Park Bo-young) of a feral and mute orphan (Song Joong-ki) who the family took in... only to discover that he was a creature never meant to exist. But damaged by life's struggles herself, the beautiful, young Suni is patiently determined to tame the "wolf boy" and teach him to live among people. In return, he repays her uncommon kindness with unparalleled devotion. When a threat to Suni brings out the boy's unrestrained, bestial instinct, he abruptly becomes the target of the villagers' fears. To save his life, Suni must abandon him, but promises she will return... Is it possible he continues to wait for her?