Cowl, the genetically modified preterhuman of the title, has travelled back to beyond the Nodus (where life first began) in an attempt to change the future of life on earth to suit his views. He checks his progress by sampling DNA from humans of the future that are bought back through time by use of a tor. These tors are distributed by the torbeast, Cowl's pet, a huge monster that has been created to travel through time at will - providing it has enough energy, which it gets from devouring humans of the future.
Of course, when something is changed in the past/future, that timeline is pushed down the probability slope. Once moving down the probability slope it requires more and more energy for a traveller to return to the correct timeline. If a traveller has gone too far down this slope, they may never be able to return to the correct timeline and be stuck in the alternate they created forever.
The story focuses on two main characters, Polly and Tack. Polly receives the tor after being pulled into the sights of U-Gov by Nandru Jurgens. Once attached to her, she starts moving back through time, jump by jump to her destination: Cowl. Tack is a programmable killer that is chasing Nandru, and in turn, Polly, trying to get that which Polly already has: the tor. He is caught in the field when Polly first moves back through time, although she manages to lose him and shift again. Fortunately (or unfortunately) for Tack, he also manages to get a tor growing on his arm and also gains the power to travel backwards through time.
Although the story may sound complicated, it is so much more readable than I was expecting. I won't go into any more details as I feel that the parts of the story that I enjoyed the most were the discoveries made while reading and trying to make sense of the information that Neal gives to the reader. It is never a dull book and is typical of Neal's action packed style.
I must admit that initially I found the character of Polly to be misplaced. A 15 year old prostitute isn't a character I expected to see in the book, but the developement is good, although perhaps hasty at the start. The development of Tack is also good and having a character that can be programmed is a nifty little idea, especially due to his role in the story.
All in all a good read and even more of a reason to pick up more books by Neal.