The time portal is disengaged, and Beckett steps out of the machine only to discover that his visit to the past has not changed the present. Many millions of people are still dying of a mysterious plague and his mission, to kill the carrier and stop the epidemic before it ever gets started, has failed. With the very survival of the human race at stake, Beckett agrees to travel back into the past again, this time one week earlier than before, to remove the person scientists now believe to be Patient Zero, a woman named Amy Barrett. But a twist of fate will alter Beckett's resolve. Instead of eliminating Amy to arrest the plague, he believes he knows a way to save the humanity of the future without harming Amy in the present. Can the fate of mankind hinge on a single act? Or are we helpless to change our destiny?