Malice steps up his efforts to find the hidden library, and Clemence and Tumi use the mole-bots to explore underground. This puts pressure on Pax to unlock the library's hidden secrets, and with Teeter's X-ray vision the gang discover a hidden room containing maps that show the location of the lost city of URBO, and a communicator that lets Pax to talk to his long-lost father. But when the mole-bots home in on the communicator's signal, Pax must abandon it to save the library.