The film revolves around the life of Dong-wook (played by Jo Sung-ha), a mentally challenged man who works at a park. He is a kind and gentle soul who is loved by everyone around him, including his daughter, Soo-young (played by Park Bo-gum). However, his life takes a drastic turn when he is wrongly accused of murdering a young girl. Despite his protests of innocence, Dong-wook is sentenced to death.