A medical mystery ... and a threat from beyond the stars.For Jon and Marianna Knox, the birth of their daughter Persephone marks the happiest day of their lives. Until they learn that Persey is suffering from a rare but fatal condition called "triploidy."Her doctors are baffled, and with good reason-because the source of the little girl's genetic malfunction is not of this Earth. It lies out beyond the orbit of Saturn.And it's coming for all of us.