But it was Wilks and Haljan in a fight up there on the cliff. The men crowded at the bull's-eye windows. And over all the confusion the alarm siren, with no one thinking to shut it off, was screaming. Grantline, momentarily stricken, stood gazing. One of the figures broke away from the other, bounded up to the summit from the stair platform to which they had both fallen. The other followed. They locked together, swaying at the brink. For an instant it seemed that they would go over; then they surged back, momentarily out of sight. Grantline found his wits. "Stop them! I'll go out and stop them! What fools!" He was hastily donning one of the Erentz suits. "Cut off that siren!" Within a minute Grantline was ready. The duty man called from the window, "Still at it, the fools. By the infernal--they'll kill themselves!" "Franck, let me out." "I'll go with you, Commander." But the volunteer was not equipped. Grantline would not wait. The duty man turned to his panel. The volunteer shoved a weapon at Grantline. Grantline jammed on his helmet, took the weapon. He moved the few steps into the air chamber which was the first of the three pressure locks. Its interior door panel swung open for him. But the door did not close after him! Cursing the man's slowness, he waited a few seconds. Then he turned to the corridor. The duty man came running. Grantline took off his helmet. "What in hell--" "Broken! Dead!" "What!" "Smashed from outside," gasped the duty man. "Look there--my tubes--" The control tubes of the ports had flashed into a short circuit and burned out. The admission ports would not open! "And the pressure controls smashed! Broken from outside!" There was no way now of getting through the pressure locks. The doors, the entire pressure lock system, was dead. Had it been tampered with from outside? As if to answer Grantline's question there came a chorus of shouts from the men at the corridor windows. "Commander! By God--look!" A figure was outside, close to the building! Clothed in suit and helmet, it stood, bloated and gigantic. It had evidently been lurking at the port entrance, had ripped out the wires there. It moved past the windows, saw the staring faces of the men, and made off with giant bounds. Grantline reached the window in time to see it vanish around the building corner. It was a giant figure, larger than an Earth man. A Martian? * * * * * Up on the summit of the crater the two small figures were still fighting. All this turmoil had taken no more than a minute or two. A lurking Martian outside? The brigand, Miko? More than ever, Grantline was determined to get out. He shouted to his men to don some of the other suits, and called for some of the hand projectors.