The rate of technical progress in the seventy years since Armstrong was enough to leave any
non-specialist hopelessly behind outside his own field, and the Geo Sciences team back at
Shepard Center had wandered down some peculiar paths to produce their current generation of
esoteric peekers and pryers. "Gravitonic resonance" was a marvelous term . . . and MacIntyre
often wished he knew exactly what it meant. But not enough to spend another six or eight years
tacking on extra degrees, so he contented himself with understanding what the "planetary
proctoscope" (as some anonymous wag had christened it) did rather than how it did it.
Maneuvering thrusters nudged his Beagle into precisely the proper attitude, and MacIntyre
bent a sapient gaze upon the read-outs. Those, at least, he understood. Which was just as well,
since he was slated as primary survey pilot for the Prometheus Mission, and—
His humming paused suddenly, dying in mid-note, and his eyebrows crooked. Now that was
odd. A malfunction?
He punched keys, and his crooked eyebrows became a frown. According to the diagnostics,
everything was functioning perfectly, but whatever else the moon might be, it wasn't hollow.
He tugged on his prominent nose, watching the preposterous data appear on the displays. The
printer beside him hummed, producing a hard-copy graphic representation of the raw numbers,
and he tugged harder. According to his demented instruments, someone must have been a busy
little beaver down there. It looked for all the world as if a vast labyrinth of tunnels, passages, and
God knew what had been carved out under eighty kilometers of solid lunar rock!
He allowed himself a muttered imprecation. Less than a year from mission date, and one of
their primary survey systems—and a NASA design, at that!—had decided to go gaga. But the
thing had worked perfectly in atmospheric tests over Nevada and Siberia, so what the hell had
happened now?
He was still tugging on his nose when the proximity alarm jerked him up in his couch.
Damnation! He was all alone back here, so what the hell was that?
"That" was a blip less than a hundred kilometers astern and closing fast. How had something
that big gotten this close before his radar caught it? According to his instruments, it was at least
the size of one of the old Saturn V boosters!
His jaw dropped as the bogie made a crisp, clean, instantaneous ninety-degree turn.
Apparently the laws of motion had been repealed on behalf of whatever it was! But whatever else
it was doing, it was also maneuvering to match his orbit. Even as he watched, the stranger was
slowing to pace him.
Colin MacIntyre's level-headedness was one reason he'd been selected for the first joint US-
Soviet interstellar flight crew, but the hair on the back of his neck stood on end as his craft
suddenly shuddered. It was as if something had touched the Beagle's hull—something massive
enough to shake a hundred-ton, atmosphere-capable, variable-geometry spacecraft.
That shook him out of his momentary state of shock. Whatever this was, no one had told him
to expect it, and that meant it belonged to neither NASA nor the Russians. His hands flew over
his maneuvering console, waking flaring thrusters, and the Beagle quivered. She quivered, but
she didn't budge, and cold sweat beaded MacIntyre's face as she continued serenely along her
orbital path, attitude unchanged. That couldn't possibly be happening—but, then, none of this
could be happening, could it?
He chopped that thought off and punched more keys. One thing he had was plenty of
maneuvering mass—Beagles were designed for lengthy deployments, and he'd tanked from the