In the series premiere, a group of five smart sixth-grade friends—Minh, Son, Sang, Quang, and Tung—embark on their first investigation when their classmate, Sinh, is robbed of 200,000 VND by a teenager armed with a screwdriver. Naming their mission "Operation TTL200", the boys use clever deductive skills, analyzing tire tracks and footprints to identify the culprit's pink bicycle and his physical limp. Their search leads them to Hai, a troubled school dropout living in a local slum with an alcoholic father