Vergil Ulam is an unconventional researcher who is working on biochips that use DNA for information processing. But he also has a private sideline which leads to his developing intelligent human white blood cells. When he is ordered to destroy his cultures he injects himself with the cells to preserve them and walks out.
The modified cells quickly take over his body, transforming it for their own purposes, and soon find a way to spread to other human beings, who begin to dissolve into vast protoplasmic sheets in which individual identity is lost. So far we seem to be reading a fairly ordinary horror story, similar to The Fly, but Bear is really writing something quite different. Before long the cells take over the whole of North America, which becomes covered with multicoloured layers of organic material in which the erstwhile human inhabitants are swallowed up. They are not destroyed but rather are subsumed into some form of universal mystical consciousness. The noocytes, as one of the characters calls them, by analogy with Teilhard de Chardin's noosphere, are not hostile to human beings and respect the wishes of those who don't want to be transformed. They also have acquired extraordinary powers: when the Russians launch nuclear weapons against America they prevent them from exploding.
For reasons that are not made entirely clear, a few people are resistant to this transformation and we witness events through their eyes as they struggle to understand what is happening. The transformation is at first confined to North America and the rest of the world tries to keep it there, but it is only a temporary respite; at the end of the book the whole population of the Earth seems to have been transmuted to a different plane of existence, leaving behind the empty shells of cities, towns, and houses. Finally the new phase of being extends outwards to envelop the whole Solar system. Indeed, will it even stop there? I think we are meant to understand that the universe is reaching Teilhard's Omega Point, a mystical and indescribable apotheosis.
This is a very ambitious book, whose theme is much larger than that of most science fiction. but for me it didn't really come off; I found the narrative to be confusing at times and I couldn't always maintain the necessary willing suspension of disbelief. There was also rather too much about Vergil, whom I found uninteresting, whereas I would have welcomed considerably more dialogue between the noocytes and one of the characters—a doctor who provides the main intellectual input into the narrative. We do get some tantalizing discussions about how the noocytes conceive of the mini-universe—the human organism—in which they find themselves, but not enough. The book does contain a lot of ideas, but I think it could have developed some of them still further.