It's 1945. Stalin calls together a group of science fiction writers and orders them to produce a scenario of alien invasion; he perceives the American threat to be on the wane, and the Soviet state needs an enemy against which to rally. No sooner have the writers developed a scenario than Stalin demands they forget the idea on pain of death. Skip to 1986, when Konstantin Skvorecky, ex-SF novelist and world-weary alcoholic now working as a translator, is approached by an old colleague who tries to convince him that their long-forgotten scenario is in fact coming to pass: aliens appear to be invading the world. What follows is in part a droll comedy of manners parodying the fall of Soviet communism, part an intellectual inquiry into the idea of multiple quantum realities and part an attempt to discover why, despite the ubiquity of reported sightings, UFOs have never been proved to exist. As ever with Roberts, the writing is impeccable and the ideas riveting.