An alien invasion...or nanotechnology run amuck? The crew of Moonbase Columbus makes 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? Is it an attempt at first contact? 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. Nebula Award nominee! "The authors have a fine grasp of character and a slick writing style."- Science Fiction Review "Anderson and Beason are the heavyweight tag-team of hard science fiction!"-Allen Steele, author of Labyrinth of Night "Wonderfully vivid, Terrifying, and worse yet ... realistic!"-David Brin, author of Startide Rising