Outbreak at the Containment Facility

The turning point of the Battle.

Events
When the Covenant accidentally released the Flood, many Covenant were killed. The Flood moved to the lower levels, keeping the top level moderatly clean.

Captain Jacob keyes, along with 2nd Squad landed nearby in Pelican dropship Victor 933 and proceeded to infiltrate the structure. They later met up with Staff Sargeant Avery Johnson's "Fire Team Charlie".

While exploring the lower levels, 2nd Squad encountered the Flood, a Corporal sent in a radio message to Johnson before being killed. The Flood on the upper levels managed to escaped and proceeded to attack Charlie. It ended with Jacob Keyes, and Charlie; with the exception to Johnson and at least 2 other Marines, becoming flood Combat Forms.

Later on, the Master Chief arrived near V933s crash site onboard Echo 419. He then entered the lightly guarded structure, being watched by the Flood. After entering the Containment Room, he found Private Jenkins' helmet with cam-corder. After seeing the gruesom events through the eyes of Jenkins, the remaining Flood spewed out of nearby doors.

After Master Chief managed to retreat to the lower levels, he discovered that the Flood had mutated the Marines, not just the Elites, even worse, they had figured out how to use weapons. After seeing the Flood kill several Marines, he carried on to an elevator, where he managed to get back to the surface, joining with the rest of 2nd Squad.

The survivors went through the swamp in search of a tower, which would be the Evac site for E419. Eventually, after reaching the tower, the Forerunner constructs known as "Sentinels," appeared and attacked the Flood. Master Chief is then teleported up in the tower by the leading construct designating itself as "343 Guilty Spark". Master Chief is then teleported away and any surviving Marines are rescued.