On a rainy night in Busan, a young woman leaves her baby outside a ‘baby box’, a safe place set up in Korean churches for new mothers to leave unwanted infants. Instead, he’s picked up by Sang-hyun (Parasite’s Song Kang-ho) who runs an unofficial adoption brokerage and plans to find him a new home. His pursuit takes an unexpected turn when the young mother tracks him and his business partner down and decides to join their journey.