A scientist develops a process for creating multiple memory timelines, allowing people to go back to unpleasant events and possibly prevent them. Individuals also remember their original timeline. As most of the world gets hold of the process, things start to go terribly wrong, and the originating scientist keeps creating new timelines in hopes of going back and preventing the horrific events from occurring. The storyline is intriguing and generally well executed, but the book is too long, and the recursions too many.