2267 A.D. The battle is won, the war may be lost. After fending off the fierce attack of Drakh combatants, Earth faces an unseen yet even greater foe - a microbial, biogenetic plague that will destroy all life on the planet in five years if a cure isn't found. Crusade follows the race against time to find that cure - an urgent and hazardous quest that sends an Earthforce expedition across the reaches of space to explore technologies more advanced than Earth's. Leading this high-stakes archeological mission is a starship of the new Interstellar Alliance, the Excalibur, and its crew drawn from the Alliance's elite troubleshooting corps, the Rangers. With 7 billion lives at stake, action and courage against insurmountable odds must prevail in this Crusade.