Without realizing why, he had obeyed to the letter the instructions of the voice on the visiphone. That single suggestion that his efforts might lead him to the murderer of his father had spurred him on. He had entered Phobos Enterprises, taken the package described. But getting away this time had been a terrible ordeal. The I.P. men were on the alert. All Crater City patrols were in readiness. The impenetration walls were down everywhere, checkerboarding the metropolis into five hundred separate and distinct guarded areas. Three times he had missed capture by a scant margin. He had crawled sixty feet through an exhaust _zordite_ tube when any second the motors leading to it might have seared his body to a crisp with their discharges. With an I.P. man close on his heels, he had swung over a dizzy canyon of space and catwalked across a sustaining bar from one building to another. And it seemed now he could still hear that cry that rose up to him on the building roof from the street below: "_Death to the Nebula!_" On the table the package for which he had risked so much lay open. Jimmy scowled down upon its contents: three Thro-Pahl figurines, gray in color, eighteen inches in height, each the likeness of an armor-clad Martian of the first dynasty. To an art collector they were undoubtedly wondrous artifacts, but to Jimmy they meant nothing. The visiphone bell sounded. Heart pounding, Jimmy touched the stud and heard again that voice. "_Good morning, Nebula. We made it this time. I'm so glad._" He stared into the blank screen silently. What did she look like, the owner of that haunting voice? Was she dark or fair? Was she...? "Who are you?" he said huskily. "There isn't time for that now, Jimmy. Tell me, have you examined the figurines?" He had the vision plate turned on, and he nodded in reply. "Look at them again. Look at their composition. It's not the carving I'm--we're--interested in. It's their structure. Don't you see, Jimmy? It's _pxar_." He didn't see, and he waited for her to continue. "_Pxar_--the same material that the engineers need for their construction work for the canal locks, the only material that will withstand the radiations of the Red Desert sands. "Those figurines are old, Jimmy. They were carved during the days of the First Dynasty when the original canal locks were built. Today there's practically none left. Yet without _pxar_ the canal project is doomed to failure. "Now pick up one of the figurines and examine its base. Do you see that tiny three-cornered prong that projects from it? Like a root, a stunted root reaching out for nourishment." * * * * *