Sang-hyeon(Song Kang-ho) and Dong-soo (Gang Dong-won) steal a baby, Woo-seong, abandoned in a baby hatch at the church Dong-soo works. They are a team of brokers, stealing babies and selling them to adoptive parents. So-yeong(Lee Ji-eun), Woo-seong's mother, shows up, asking to get her baby back, but she agrees to go along to find new parents for the baby.
However, two police detectives, Soo-jin(Bae Doona) and detective Lee (Lee Joo-young) are following them, in order to catch them selling the baby red-handed.
Broker contains examples of:
- The Alleged Car: Sang-heyon's van is so old and broken that the back door doesn't close properly.
- Baby as Payment: The titular brokers make money by selling infants to parents who want to adopt.
- Cluster F-Bomb: So-yeong lets out a string of curses at a couple looking to buy Woo-seong, because they tried to haggle down the price, saying Woo-seong was ugly.
- Don't You Dare Pity Me!: So-yeong gets mad when detective Lee asks if she was forced into prostitution, and angrily asks detective Lee if Lee is pitying her.
- Doorstop Baby: So-yeong abandons her baby in front of Sang-hyeon and Dong-soo's church. Detective Soo-jin goes and puts the baby in the baby hatch, so he won't freeze to death.
- Inspector Javert: Soo-jin is more concerned with catching her mark than for the well-being of the child. She does not care about Woo-seong's health when he gets sick, and even tried to set up Sang-hyeon to sell the baby, just so she could get an arrest under her belt.
- Meaningful Name: Woo-seong means "winged star". So-yeong says she gave him the name in the hopes that he gets to rise up high.
- Parents for a Day: The protagonists take care of Woo-seong until they can sell him to the highest bidder.
- Pull the Thread: Dong-su discusses various infertility treatments with a fake couple looking to buy the baby. When the fake husband says he has been taking medication for ovulation, Dong-su calls him out on lying and calls off the deal.
- Road Trip Plot: The protagonists drive around in their van, and later take a train, on a journey to find new parents for Woo-seong.