The greatest scientific challenge of our age wasn't to enable time travel, it was to prevent it. The laws of physics had turned out to be idiotic, erecting no barriers to hopping time. In fact, they make it hard to avoid. I'm in the business of preserving the timeline—making sure the world sticks to the sacred rule of One Second Per Second, and that history unfolds according to plan. The problem is, there is no plan until I make it.