343 Guilty Spark is the sixth campaign level in Halo: Combat Evolved. It takes place on Installation 04 Flood Containment Facility. In this level, John-117 is dropped from Echo 419 to search for Captain Keyes. Soon, the Master Chief stumbles upon a structure and ventures within it, only to find out that the Marines accompanying the Captain have been slaughtered by the Flood. After realizing the fate of the Marines, John fights his way out to the swamp and encounters a questionable ally.