The great sunliner 'But the Sky, My Lady! The Sky!' is nearing the end of a four-hundred-year journey. A ship-born generation is tense with expectation for the new system that is to be their home. Expecting to find nothing more complex than bacteria and algae, the detection of electronic signals from one of the planets comes as a shock. In millennia of slow expansion, humanity has never encountered aliens, and yet these new signals cannot be ignored. They suspect a fast robot probe has overtaken