Despite the disbandment of Rainbow Taxi, Do-ki is still out there going after bad guys. While keeping it from the rest of the members, Do-ki and Sung-cheol secretly help out a father who is searching for his missing son. To confirm his whereabouts, Do-ki sets off abroad to a foreign country to accomplish his first mission.

Do-ki successfully infiltrates Cheongeum with the help of his old crew. He pretends to be an abducted recruit but secretly searches for Dong-jae. During the search, he runs into Lim Bok-ja. He uses her revengeful anger to make it easier to find the missing boy. Just when he is about to capture the mastermind, a mysterious gun shot interrupts his arrest.