Fleeing a world consumed by the ravenous, alien Swarm, the heroes and a handful of desperate survivors limp toward the nearest colony world in a newly acquired starship. After thwarting a mutiny, they reach a large metropolis, where tensions are high. Local fanatics claim the oncoming Swarm is a punishment for the system's sins, disrupting the military's efforts to take in refugees. Worse, a series of caverns below the city that provide the only refuge from inevitable invasion are far from unoccupied, and must be cleared out before time runs out!