Spartakus and the Sun Beneath the Sea

While exploring a cave, Matt and Rebecca meet Arkana, who tells them of her mission. When the pirates attack, they are rescued by a mysterious warrior named Spartakus.

Tehrig is swept away by the powerful currents of the River of Time. The group finds themselves in a land occupied by a primitive tribe that is being threatened by the machines of an advanced civilization from the stratum above. Meanwhile, the children of Arkadia are trying to fix the entrance to the Archives, which has rusted shut.

Arkana is kidnapped by the Thot, a gigantic, well-meaning beast who lives in an abandoned metropolis.

The group returns to Arkadia to attempt to free the Prisoners of Lost Time but discover that the Tehra will never be permanently restored until a riddle is solved and a second auracite is found.

The group is forced to battle in a real-life chess match against some of their most fearsome enemies.