Z-DAY ON CENTAURI By HENRY T. SIMMONS Erupting from hyper-space in the teeth of startled DIC patrols and readying all hands for a crash-landing, adventurer Fletcher Pell could still wonder which he dreaded more--the U-235 in the hold ... or the strange girl by his side. [Transcriber's Note: This etext was produced from Planet Stories Summer 1948. Extensive research did not uncover any evidence that the U.S. copyright on this publication was renewed.] Pell twisted into the black maw of the alley and ran silently and swiftly into its depths. His breath came in whistling agonized gasps. Faintly he heard the footsteps of his assailant--now more clearly as the latter turned into the alley after him. Vaguely Pell could make out his silhouette outlined by the dim light that filtered in from the street. "Ugh!" Pell struck a hard surface at the end of the alley with a grunt that he could not stifle. Trapped! Frantically he felt about to find an opening. Softly and steadily he cursed himself, trying to keep black despair at bay. Maybe if he ... but the idea died in birth. "Chuu!" A blue lancet of flame arced over Pell's shoulder and struck the wall, turning a small area into running slag. The heat and prickling of the radiation Pell ignored. But the brief flash had given up his position. Then he heard his pursuer laugh softly and he knew the game was up. He felt rather than heard him moving in. _Paumm!_ Pell's universe rocked in the reverberating thunder of the explosion. _Paumm! Paumm!_ Twice more it was repeated and in the vivid flash Pell saw his assailant twist and collapse on his face. His amazement fought with a new dread. Someone had come to his aid, but with an ancient, chemical-reaction, hand weapon. What did that mean? With his back tensed against the wall, Pell strained his perceptions to the utmost, trying to adjust his eyes once more to the darkness. Then he jumped. "Pell!" It was a woman's voice! "Fletcher Pell! Come out--I am a friend!" He was aware of a faint outlander quality in her accent--as if she were a colonial. Dimly he could make out her slight figure at the mouth of the _cul de sac_. He moved cautiously toward her, stopping to pick up the blaster of the fallen DIC agent. The comforting feel of its butt gave him confidence as he walked toward her. "Who are you?" Pell asked. She was small and lithe, and in the dim radiance of the street lights he noticed that she had brown hair with glints of spun-gold in it. She did not reply to his question but put a soft hand over his mouth. "Let your questions wait. We must leave quickly, else they find us," she said huskily. She led him from the alley and walked breathlessly down the dark street, two of her steps matching one of his long ones.