It was the jewel-box that held Tumek's crystal. Zenaor's fists clenched. "Curse you, Vydys--!" She turned away as if he had not spoken. Smiling at Craig, she purred, "A last chance for you, Earthling. Would you join me?" Craig's eyes met Narla's. Then, quietly, he said, "You know my answer, Vydys." Her face contorted. "Die, then, you fool!" She started to turn back to Zenaor. Only then, incredibly, a fire-gun was in his hand, too, whipping up from beneath his scarlet cloak. They fired together. Vydys screamed in the same instant. For the fraction of a second green flame seemed to envelope her. A great black char-scar spread across her naked belly. She tottered. Her guards lunged forward. But already Zenaor was leaping into the laboratory chamber. Headlong, he dived for the transparent cubicle in the center and wrenched its hatch open. * * * * * Like a wave of slime, the ourobos belched forth, spilling across the floor in a hideous, writhing blot. The foremost of Vydys' charging guards screamed and tried to stop. Too late. He pitched into the fungous tide; screamed just once more. A bubbling scream.... The room erupted into chaos. Alike, Vydys' men and Zenaor's fled in shrieking panic. Craig thrust a foot across one's path; snatched a fire-gun as the man fell sprawling. The room was empty, then ... empty save for dead Vydys and her guard, and Zenaor, and Narla, and Craig Nesom. And the ourobos. Coolly, Zenaor stood his ground beside the cubicle. Ourobos swept in close about his feet, then eddied back. They would not touch him. He laughed; gestured. "You see, alien? The tanagree oil is in my veins; they will not touch me. But you...." He laughed again. Craig said, "Much good may it do you, Zenaor. A corpse is a corpse, even if the worms won't eat it." He raised the fire-gun. Zenaor's laughter died. He half-turned. "Wait, Earthman--" He whipped up his own weapon. Craig fired. Zenaor died. Then Narla was in the Earthman's arms again, heedless of the ourobos' creeping tendrils. "So we die, Craig Nesom. But at least we die together." Craig held her close. "No, Narla." "No--?" He could feel her body stiffen. "But--what--?" "I said no, Narla. We don't die. Neither of us." She stared at him. He said, "Don't you see? The ourobos--they're thallophytes. That's the answer." And then, when she still showed no comprehension: "Tumek knew. That's why he said his crystal was the only weapon that would stop them. And Bukal hit it right--by accident--when he looked at the thing and said it might as well be a lamp-lens." "Craig, I don't understand--" "I'll show you." Pushing the girl back, Craig took the jewel-case from the table where Vydys had tossed it and crossed to the nearest lamp ... carefully replaced the focus prism with the crystal. The beam sprayed out, all green and purple. Tilting the lamp, Craig brought it to bear on the encroaching slime of the ourobos.