"Virgil's back!" he exclaimed.

Pete Graham didn't even hear the sound of his heavy coffee mug as it struck the floor. By the time the liquid spilled, he was already bolting out the door. What he found made Pete Graham's heart soar.

Standing in the shade beside the trailer, the majestic backdrop of Popocatepetl rising high above all, was his precious Virgil probe. Somehow, in defiance of all programming and human logic, his baby had come home.

Behind Graham the other scientists, along with Clark Beemer, were hurrying down from the trailer. Pete Graham didn't even hear them. Like a fretting mother, he carefully circled the probe.

When standing upright, Virgil was roughly seven feet tall. Squatting now, it was only five feet. Its eight mechanical legs were curled beneath the hard shell of its silver-plated thorax.

Graham noted a set of big spidery tracks running from the lava-formed gorge a dozen yards away from the trailer. His amazed eyes tracked the furrow up to the parasitic cone in the wounded side of Popo.

"He must have climbed out after he lost contact with us," Graham said, bewildered. "He used the cone as an exit and somehow followed the gorge to us."

The rest of his team had clustered at an awed distance. Only Clark Beemer had the temerity to speak. He had gotten over his initial shock and was now shaking his pant legs in a vain attempt to dry the urine stains.

"Is it a homing probe?" the PR man asked absently.

"Don't be an idiot," Graham said.

He was studying the clean silver surface of the Virgil probe. There wasn't so much as a scratch or dent in the smooth heat-resistant plating. Even more, Virgil wasn't even dirty. Despite its stay in the volcano crater and its trip down the muddy lava gorge, there wasn't the slightest visible hint of the punishing ordeal it had been through.