McCauley uttered some profane words in the close confines of his space helmet. Back at Lunar Base he'd laid the matter of Holmes and Kent before the commanding officer, who was the ranking officer on the moon. Kent was an able young officer, transferred to Space Service from the Air Force. Holmes was also an able young officer, who'd been a submariner before he transferred to the equally confining Space Service. They'd known each other back on Earth and somehow--nobody knew how--a bitter and inveterate enmity had sprung up between them. Perhaps a girl was at the root of it, but if so, neither of them won her. Perhaps, by this time, the initial cause of their hatred had nearly or completely ceased to matter. Enmity does not often last unless things occur that can feed and strengthen it. It is normal for two young men to quarrel furiously and be ready to kill each other. But if they are separated long enough, their hatred usually dies away to acute dislike. In time the dislike fades to mere aversion or they may forget their anger altogether. But this happens when there is nothing to sustain and increase the quarrel. On the other hand, if they come across each other often enough, and more especially if they try to harm each other, what could have begun as mere indignation and contempt can build up into a blind and murderous fury at the mere sight or thought of each other. How it started does not matter then. McCauley suspected that this was the case with Kent and Holmes. Swinging up and soaring ahead, touching ground with precision at each landing and swinging up again to strange, wingless flight, McCauley muttered to himself. They'd been assigned to his command. Not knowing--then--he'd introduced them. They spoke with great politeness but did not shake hands. Settling down to the routine and tedium of a six-man base, it became evident that there was something wrong. There was no overt trouble, but there was strain. It showed in a thousand trivial ways. When a party went out on an errand which required traveling for days in roasting sunlight, cased in space suits that were almost as confining as strait jackets, under conditions which rasped the nerves and tried the tempers of everybody, Holmes and Kent very nearly caused disasters.