Years ago, the Locust Horde gathered under every major city and launched a surprise attack. Once thought fictional boogeymen, the Horde are frighteningly real and stronger than anyone had imagined.
On Emergence Day, untold masses perished, and countless more died in the days that followed. Rather than allow the Horde to keep the spoils of their aggression, humans used chemical weapons and orbital particle beams to neutralize them, along with the cities and bases they controlled.
With most urban centers and military installations rubble, the human survivors gathered on Jacinto Plateau, whose solid granite strata could not be easily penetrated. When the Horde breached the plateau's defenses, Marcus Fenix defied orders to save his father at East Barricade Academy ... but he was too late. Marcus was subsequently charged with dereliction of duty and sentenced to 40 years in Jacinto Maximum Security Penitentiary.
Now, the Horde have overrun the penitentiary.