This two-hundred-year war has taken its toll, and many lives are lost, along with the destruction of most of the environment on two planets. Many from both sides are tired of the fighting and want to stop the war, but neither knows how. Then Professor De'Zane produces an idea. "Instead of ending the war, why not stop it before it begins?" Unfortunately, Earth does not have the technology, but the Tharoans do.

This tale begins with the destruction of a Tharoan ship as it comes through a wormhole over a deserted island where the United States is conducting a nuclear test. Their civilization takes this as an act of war, resulting in the attack on Earth lasting two hundred years.

The President of the United Earth orders Admiral Hawkens and the crew of the UES Galaxy to travel back in time to stop the war at any cost. One major problem, they can't kill anyone from the past for fear of disrupting Earth's timeline.