There was a flurry of tigers, but they were larger animals and were promptly shot down. They prowled at night, so the colonists were assigned to guard the settlement around the clock. Where lights failed to reach, the infra-red 'scope did. As fast as they came, the tigers died. Except for the first one, not a single dog was lost. The tigers changed, though not in form. Externally, they were all big and powerful killers. But as the slaughter went on, Marin noticed one astonishing fact--the internal organic structure became progressively more immature. The last one that was brought to him for examination was the equivalent of a newly born cub. That tiny stomach was suited more for the digestion of milk than meat. How it had furnished energy to drive those great muscles was something of a miracle. But drive it had, for a murderous fifteen minutes before the animal was brought down. No lives were lost, though sick bay was kept busy for a while. That was the last tiger they shot. After that, the attacks ceased. The seasons passed and nothing new occurred. A spaceship civilization or even that fragment of it represented by the colony was too much for the creature, which Marin by now had come to think of as the "Omnimal." It had evolved out of a cataclysmic past, but it could not meet the challenge of the harshest environment. Or so it seemed. * * * * * Three months before the next colonists were due, a new animal was detected. Food was missing from the fields. It was not another tiger: they were carnivorous. Nor rats, for vines were stripped in a manner that no rodent could manage. The food was not important. The colony had enough in storage. But if the new animal signaled another plague, it was necessary to know how to meet it. The sooner they knew what the animal was, the better defense they could set up against it. Dogs were useless. The animal roamed the field they were loose in, and they did not attack nor even seem to know it was there. The colonists were called upon for guard duty again, but it evaded them. They patrolled for a week and they still did not catch sight of it. Hafner called them in and rigged up an alarm system in the field most frequented by the animal. It detected that, too, and moved its sphere of operations to a field in which the alarm system had not been installed. Hafner conferred with the engineer, who devised an alarm that would react to body radiation. It was buried in the original field and the old alarm was moved to another. Two nights later, just before dawn, the alarm rang. Marin met Hafner at the edge of the settlement. Both carried rifles. They walked; the noise of any vehicle was likely to frighten the animal. They circled around and approached the field from the rear. The men in the camp had been alerted. If they needed help, it was ready.