EonAbove our planet hangs a hollow Stone, vast as the imagination of Man. The inner dimensions are at odds with the outer; there are different chambers to be breached, some containing deserted cities; and the furthest chamber contains the greatest mystery ever to confront the Stone's scientists.EternityHere, from the other side of time, come: THISTLEDOWN, the asteroid starship of a future that is not quite our future; GAIA, a parallel reality where Alexander the Great's empire has ruled for two thousand years; and THE WAY, an infinite corridor through space-time which traverses and encompasses whole universes. And as the strands of these mysteries are unravelled, so the ordering and the end of mankind -- and our entire Universe -- come into question.