It is some time after Ed Chianese''s trip into the Kefahuchi Tract. A major industry of the Halo is now tourism. The Tract has begun to expand and change, but, more problematically, parts of it have also begun to fall to earth, piecemeal, on the Beach planets.We are in a city, perhaps on New Venusport or Motel Splendido: next to the city is the event site, the zone, from out of which pour new, inexplicable artefacts, organisms and escapes of living algorithm - the wrong physics loose in the universe. They can cause plague and change. An entire department of the local police, Site Crime, exists to stop them being imported into the city by adventurers, entradistas, and the men known as ''travel agents'', profiteers who can manage - or think they can manage - the bad physics, skewed geographies and psychic onslaughts of the event site.But now a new class of semi-biological artefact is finding its way out of the site, and this may be more than anyone can handle.