"You will find a metal disk in the exact center of the wall," the Ganymedean explained hurriedly. "Blast it with your electro-beam. It is the mechanism of a door, the combination to which we do not possess. Be prepared to _destroy instantly everything that meets your eyes_--everything!" He motioned for Julian to enter the tunnel. "You will have only seconds to achieve your purpose. And remember, your life's already forfeit, so do not hesitate now!" "But what _is_ behind that door?" Julian asked, exasperated. "I have a right to know!" He laid a detaining hand on the Ganymedean's shoulder. "_I must know!_" By the spectral radiance of the pencil-beam, the artist eyed Julian with a strange expression in his eyes. "As you will, Dekkan," the being shrugged his shoulders. "You will find a laboratory ... if you live to reach it. It is doubly guarded, although even the Dynasty does not suspect the existence of that door, for it is part of the remains of our own subterranean system. Beyond it ..." the Ganymedean paused, "in that laboratory is stored the blood-plasma of Mutants who have voluntarily submitted to _innoculation with a certain disease_. The resulting modified virus is the _Plague_. It's like a vaccine magnified a thousand times--its victims do not die, they merely become _sterile_!" The Ganymedean turned toward where the corridor curving to the right was lost to view. "I go that way," he said simply. "My place is here." "But ... your message on the disc ... you mentioned Rohan Square!" Julian exclaimed. "If I survive this, how can I...." "_You are standing beneath Rohan Square, and the Temple, Dekkan!_" And that was all. Suddenly he was gone like a wraith that melted into the darkness and the silence, his footsteps muted by the velvet carpet of dust. Julian hesitated no longer. He found the metal disc in the wall, and with the "electro" at low power destroyed the ancient mechanism of the door. As if released from the bond that for so long had held it, the great section rolled back with a crash, carrying away with it a jagged section of plastic covering from its other side. Julian had a vivid glimpse of startled, silver-haired technicians who stared unbelieving at the strange apparition. In that dazed moment of inaction, Julian acted. _He was in!_ The lethal power of the electro-beam in his hand swept like a scythe through the group of Mutants. It was ghastly. The blasted sides of culture vats poured their viscous contents on the floor. There was a livid, billowing flare of incandescence as acids were struck. It was a welter of destruction and supernal fire that roared into the laboratory before any of the Mutants had a chance to act. The acrid smoke, the odor of disintegrated flesh was like a heavy pall. Through it, galvanized figures could be seen descending a winding staircase that led upward from the subterranean lab. The Guards! V