After learning of the Hypernauts (from their first encounter with Paiyin), the Triiad have activated and englobed the central region of the Milky Way Galaxy in a sensor net called "The Sphere of Interception," which can identify any end-to-end destination point for any hyperspace jump passing in and out of it (which includes any form of communication) so returning/calling home would lead the Triiad directly to Earth. The Hypernauts must keep the location of Earth a secret and somehow try to warn Earth of the Triiad's existence.