Alcatraz Asteroid was a separate world, an island of rock, wedge-shaped, eighteen miles long, and roughly the same in the circumference of its larger end. The interior was not hollow, but was honey-combed with habitable caverns like large bubbles, connected by a maze of passages. Outer levels had all been converted into a prison without guards and without bars. Life was easy, the social structure simple, idyllic or primitive depending upon the point of view. Though not completely self-sufficient--since enlightened penology provided lavish supplies--the convict community would have gone on much the same if the rest of the Solar System had suddenly ceased to exist. Elementary machinery for the basic trades had been provided; its use or neglect was left up to the prisoners. By artificial illumination, food could be grown in subsurface hydroponic gardens, and limited animal husbandry was encouraged. But lack of usable fuels and raw materials limited manufacturing to safely low levels, which prevented even gifted technicians from getting ideas. Potentially fissionable ores were present in the deep interior, and under pressure someone might have found ingenuity to process it. Air and water were hermetically sealed-in, automatically purified and reclaimed at need. Convicts were self-governed, which meant a rule of claw and fang since weapons were crude and hand-made. Dwelling in caves, the prisoners returned to an archaic way of life and became cave men. Life was brutal, direct, and usually brief. Cowards rarely got there, and the weak and unfit were quickly weeded out by living conditions intolerable to endure. Survivors were a tough, rangy breed who would survive anywhere. The few women were rank weeds, not delicate flowers; if they did not thrive, they persisted. Some children were born, and those who lived grew up as sinewy, strong and poisonous as desert snakes. At the time the asteroid had been converted to a prison, it was assumed that it was uninhabited. But laired deep within the poisonously radioactive caverns was a small colony of the legendary lost race of Pit Men. Underworld legends told in whispers that these eery creatures sometimes came from their lairs and mingled with the human convicts of Alcatraz. Actually, prisoners rarely encountered them, for the Pit Men were shy, nervous beings, harmless unless provoked, and did not issue from their caverns except by stealth for provisions. The aboriginal dwellers were neither man nor bird, though they resembled both superficially. They were non-human, non-animal, being plants, mobile and intelligent, a variety of animated fungus so alien that contact on any but the simplest levels was impossible. Even so, they were the one fly in the ointment--