Yauna Collin is the so called 'Amateur Sleuth' because of her extraordinary skills in solving mystery cases. Now, her body was nowhere to be found. The Young Detectives' Coterie is suffering because her sudden absence left a void in the group. Until one day, Yauna's comrades encountered a young girl solving a simple mystery situation. The way she solved the mystery, the way she talked and even the gestures were very Yauna Collin. The young girl, Ellen, was then spilled out the 'truth'--that Yauna Collin possesses her body or in other words, Yauna is inside the girl's body. To clear things out, the adviser of YDC, Sir Lawhiro, conducted the Test of Critical Thinking to prove if she really is Yauna. and together with the other Young Detectives, they will search and find for Yauna's body.