He looked around carefully to get his bearings, then submerged again. The opening into the ancient sewer was nearby. Once into that network, he would know exactly where he was heading. It had taken weeks to find his way around within the unexplored maze of the old sewers, and he had been uncertain whether they would lead him to the place he intended to visit, but luck had been with him. Now he knew exactly where he wanted to go, and exactly what he would find there. He had avoided Government City itself since his first appearance there, shortly after his arrival, just as he had, as much as possible, avoided ever striking in the same place more than once. But now that it had become necessary, he went about his work with the same cool determination that had always marked his activities. He knew his destination, too. He knew the two rooms thoroughly, having explored them carefully and gone away undetected. And now that he knew the one he sought was in those rooms, he was ready to make his final investigation of the man. He swam on through the utter blackness of the brackish water until his head broke surface again. Then he went on along the great conduits that were above the level of the sea. * * * * * Captain Davidson Greer sat in the gun tower that overlooked the Officers' Barracks and the courtyard surrounding the five-story building. He was a tall, solidly built man in his early thirties, with dark gray-green eyes and dark blond hair. He didn't particularly care for gun-tower duty, but this sort of thing couldn't be left to anyone who was not in on the secret of the Nipe. As long as Colonel Mannheim was here in Government City, there would be special officers guarding him instead of the usual guard contingent. Not that Captain Greer was actually expecting the Nipe to make any attempt on the colonel's life; that was too remote to be worried about. But the gun towers had been erected fifty or more years before because there were always those who wanted to attempt assassination. Officers of the World Police had not enjoyed great popularity during the reconstruction period after the Holocaust. The petty potentates who had set themselves up as autocratic rulers in various spots over the Earth had quite often decided that the best way to get the WP off their backs was to kill someone, and quite often that someone was a Police officer. Disgruntled nationalists and fanatics of all kinds had tried at various times to kill one officer or another. The protection was needed then. Even now there were occasional assassins who attempted to invade World Police Headquarters, but they were usually stopped long before they got into the enclosure itself. Still, there was always the chance. There had been, in the past few years, an undercurrent of rebellion all over Earth because of the Nipe. The monster hadn't been killed, and there were those who screamed that the failure was due to the inefficiency of the Police.