When Billy was sixteen years old, his life changed forever.

Billy had attained the normal stature of an average sixteen-year-old. His unlined, emotionless face was attractive in the manner of a well-designed mannequin. His narrow crescent of hair, kept neatly trimmed by his mother, was a common brown. His eyes remained the same empty mint-green pools.

Each morning Billy's mother removed him from bed. She took off his pajamas, bathed him, dressed him in pants and shirt, socks but no shoes, and fed him. (Billy had progressed to solid food at the appropriate stage in his development, mastication apparently being as instinctive as suckling, and within his limited capabilities.) Then she sat him down in a comfortably padded chair and left for work. Billy's muscles were kept well-toned by a series of exercises which his father put him through each night, and he would maintain whatever pose he was arranged in.

Billy's mother knew she could leave her son safely alone while she worked, for he would make no movement of consequence to endanger himself. The only thing she worried about was a spontaneous fire of some sort, in which case Billy would continue to sit until consumed. (Billy's reaction to even a pinprick was nil.) But after installation of an elaborate fire alarm system and a machine that would automatically dial 911, she managed to rest easy.

Occasionally Billy's mother would leave the TV on for him, knowing full well that it made no difference, but somehow feeling better for doing it.

On this fateful day, the television was not on. Therefore Billy sat in complete silence. Time passed. Morning shadows lengthened into those of the early afternoon. Billy sat as his mother had left him. He did not stir, save to blink now and then. His heart beat. His lungs worked. The few neurons he owned discharged in their efficient, albeit limited fashion.

Directly above Billy's head, a spider was attached to the ceiling by her thread. She was a rather large black spider, of a mundane household species, but about the size of a ping-pong ball. Although Billy's mother was a good housekeeper, she had somehow missed this spider in her weekly cleaning.

The spider was very intelligent, as were most members of her species. Contemplating Billy's gaping skull below her, the spider reached the conscious decision that the inside of Billy's head represented a safe and attractive place to build a web.

The spider began to descend, letting out silk in her judicious way.

She paused a few inches above Billy's open pate. From this vantage, the place still held its appeal.

The spider entered Billy's skull.

When her legs touched Billy's bare brain, Billy's limbs twitched. The spider cut her silk. She looked around. The place was pleasantly confined, yet open to passing insects.

"This is a good place to build a web," she said aloud, to herself.

Then she began to spin a web, parallel to the base of Billy's brain, and anchored to the sides of his skull.

Since the spider did not again touch Billy's brain, he did not move.

When Billy's mother returned that night, the spider's web was complete.

Billy's mother did not notice, since she had long ago ceased to look inside Billy's head.

When supper was ready, Billy's mother brought him to the table.

The spider was initially somewhat alarmed when her new home began to move. But since the movements were gentle, and her web was not threatened, she eventually accommodated herself to the notion that her web was now mobile. It seemed an advantage, in that more territory would be open to her predations.

Billy's father, massaging and exercising his son's limbs later that night, also failed to perceive the new occupant of his son's skull.

Thus a new symbiosis was achieved with little difficulty. For the next few weeks, the spider lived a pleasant life, alone in Billy's skull. She caught bugs. She ate them. She slept. Billy's exterior life did not change.