Lee Gang Sik (Cha SeungWon) is serving a life sentence for murder. For the last 15 years, he has been on his best behavior, and now his wish has finally come true. Gang Sik has been granted a one-day leave to visit his family, and as the day draws closer and closer, he is overcome with both excitement and nervousness. There is so much he wants to say to his teenaged son (RyuDeokHwan), whom he hasn't seen since incarceration, but the feeling isn't exactly reciprocated. Forced to grow up at an early age, his son has had a tough life, taking care of his troubled mother on his own, and in his eyes, he sees not a father, but a stranger, a criminal. How can Gang Sik make up for 15 years with just one day's time?