Now, with Dark Light, MacLeod delves further into a human future crammed with innumerable varieties of intelligent alien life. For intelligence, it turns out, is rare -- on planetary surfaces. It is ubiquitous everywhere else, from the Oort-cloud fringes of star systems to the magma furnaces beneath planetary crusts. Among the powerful intelligences that pervade the universe, there are profound differences of opinion about how to deal with surface life-forms such as human beings.