The C21 Special Task Force follows five middle school friends - Minh "the Owl," Sơn "Brainy," Sáng "Chubby," Tùng "Skinny," and Quang "Basket" - who share a passion for detective work. Together, they form the C21 Special Task Force, using their intelligence, courage, and keen powers of deduction to investigate mysterious incidents and solve challenging cases. Despite their young age, the team repeatedly cracks important mysteries, helping protect the peace and safety of both their school and the neighborhood where they live.