Tim returns to school, but he is behaving strangely. Discovery of the tunnel puts the Unlisted in jeopardy, and the twins have to decide whether they can trust their Bua when she accepts a job with the GCI.

Jiao earns the twin's trust when he helps them out of a sticky situation, but his intervention rouses the suspicion of class bully Regan. A field trip to GCI headquarters sees the boys entering the lion's den.