After a seemingly harmless explosion takes place over the Alaskan Peninsula on the eve of the 22nd century, almost 30 years since mankind quelled the Sirujian invasion, a frightening phenomenon springs up across the planet. People grow ill and die in droves, the incurable strain known as the Judgment Plague purposefully mutating itself to target the weaknesses of its host. With the Judgment Plague (believed to be of Sirujian origin) devastating Earth's population, a group of soldiers and scientists, funded by billionaire entrepreneur Eric Watkins and led by the only people who've been to Xavier before, must return to the infamous planet in search of information they hope will lead to a cure.

Yet despite the incredible measures they have taken, this group could never have prepared themselves for what they must face when they arrive. The tribes, no longer under Sirujian rule, are in chaos. The Sirujians, thought to be defeated, still guard their planet, while mutiny and personal agendas threaten to tear the group apart from the inside. Yet even more dangerous is the very thing they seek. The Lost Tribe, a hypothetical, almost mythical species thought to have been destroyed by the Sirujians thousands of years ago, may have been given the Scroll that documents the Judgment Plague. Despite this, these creatures and their elusive history could prove to be a bigger threat to mankind's survival than the Sirujians ever were.

Returning to Xavier is simple. Leaving it again, however, may be impossible.