A covert military unit discovers that extraterrestrial entities have replaced soldiers within the Army's ranks, disguising themselves as ordinary personnel. Players command this specialized task force through intense combat zones to root out the alien impostors before they can consolidate their foothold on Earth. Along the way, operatives must scavenge for advanced weaponry, liberate captured hostages, and navigate relentless waves of hostile creatures determined to overwhelm them. Success means humanity's survival; failure means assimilation into the very alien force they're fighting against.