Called to check on an anomalous occurrence at the White House, a group of scientists from an institute in a mid-twentieth century universe have a deadly encounter with the Khysids. Like a modern Prometheus, the scientists steal Khysid technology and with the help of a former Khysid operative discover how to create a Source Gate. Hounded by a rogue Army general and hunted by the Khysids, the scientists flee to the 1861 universe and the Civil War. There they are first captured then sheltered by Colonel Crittenden of the Confederate Army.
The scientists have upset Khysid plans and now the invasion begins. Both the Union and Confederacy learn the fate intended for them, one with a special irony for the South. The Khysids treat war as an amusing game and the scientists will simply serve as additional fodder, or so they think. But these unusual newcomers have upped the stakes by forcing the two combatants to fight as one. By using their skills to bring technology into the 1861 universe to counter the Khysids, the scientists have halted the invasion. But the war is just beginning and it may be the Khysids who will become history.