The plot is about the “Grail War,” mistakenly copied from Fuyuki’s Third Grail War. After the end of the Third Grail War, members of a magical organization in the United States, independent of the London Mage Association, collected data about the Grail War in Fuyuki and plan to begin their ritual. After seventy years of planning, they selected the city of Snowfield in California, north of Las Vegas, as the Sacred Ground for conducting their own Grail War. The surrounding forests, swamps, valleys, and deserts were considered favorable for the ritual.
However, they were unable to successfully reproduce every aspect of the ritual, so it did not result in a full Grail War, but only an imitation. For this reason, the Saber class was lost, and the concept of a “hero” was erased—making possible the summoning of unusual Servants. (c)