When winter came the invaders retired and the farmers went back to their fields. In the spring they ploughed and sowed as of yore, and watched in hope the growing crops. But with the summer the Spartans came again, to destroy their hopes of a harvest, and the country people once more fled for safety to their great city's defiant walls. It was a strange spectacle, that of a powerful invading army wreaking their wrath year after year on deserted fields, and gnashing their teeth in impotent rage before lofty and well-defended walls and ramparts, behind which lay their foes, little the worse for all that their malice could perform. Athens felt secure, and laughed her enemy to scorn. Unhappily for her, a new enemy was at hand, against whom the mightiest walls were of no avail. Sparta gained an unthought-of ally, and death stalked at large in the Athenian streets, silent and implacable, without clash of weapon or shout of war, yet more fatal and merciless than would have been the strongest army in the field. Athens was crowded. The country people filled all available space. There was little attention to drainage or sanitary regulations. An open invitation was given to pestilence, and the invited enemy came. For some years before the plague had been at its deadly work in Egypt and Libya, and in parts of Persian Asia. Then it made its appearance in some of the Grecian islands. Finally its wings of destruction were folded over Athens, and it settled down in terrific form upon that devoted city. The seeds of death found there fertile soil. Families were crowded together in close cabins and temporary shelters, to which they had been driven in multitudes from their ravaged fields. The plague first appeared in mid-April in the Piraeus,--brought, perhaps, by merchant-ships,--but soon spread to Athens, and as the heat of summer came on the inhabitants of that thronged city fell victims to it in appalling multitudes. The plague, they called it. The disease seems to have been something like the small-pox, though not quite the same. Its victims were seized suddenly, suffered the greatest agonies, and most of them died on the seventh or the ninth day. Even when the patients recovered, some had lost their memory, others the use of their eyes, hands, feet, or some other member of the body. No remedy could be found. The physicians died as rapidly as their patients. As for the charms and incantations which many used, we can scarcely imagine that they saved any lives. Some said that their enemies had poisoned the water-cisterns, others that the gods were angry, and vain processions were made to the temples, to implore the mercy of the deities.