Duncanville centers on the life of Duncan Harris, an average 15-year-old boy, who is always one step away from making a bad decision. Along with Duncan lives his mom, a parking enforcement officer, who dreams of being a detective someday and always has to watch Duncan; his dad, who tries to be a better father figure to Duncan than his father was to him; his sister Kimberly, who is a normal teenager going through normal teen-phases; and his other adopted sister Jing, who is an intelligent 5-year-old always giving Duncan advice. Mia is Duncan's on-and-off crush.