Nebula Award Nominee. The crew of Moonbase Columbus make an amazing discovery on the far side of the Moon—a massive alien structure is erecting itself, built up atom by atom by living machines, microscopically small, intelligent, and unstoppable, consuming everything they touch. The mysterious structure begins to expand and take shape, and its creators begin to multiply. Is this the first strike in an alien invasion from the stars? Or has human nanotechnology experimentation gone awry, triggering an unexpected infestation? As riots rage across a panicked Earth, scientists scramble to learn the truth before humanity’s home is engulfed by the voracious machines.