This article is about the campaign level. For other uses, see Flood (disambiguation).
Following Professor Ellen Anders' transponder signal, Spartan Red Team crashes their Warthog about a hundred yards from the signal, near several Flood colonies and a Proto-Gravemind. After the crash, Captain James Cutter contacts Sergeant John Forge at a nearby firebase and orders him to rendezvous with Red Team and to find Anders. After building up his forces, Forge leads an assault to link up with Red Team, only for the transponder signal to stop broadcasting as it was being duplicated by the Proto-Gravemind to trick the UNSC forces. Together, Red Team and Forge's forces kill the Proto-Gravemind.
With the Proto-Gravemind dead, Serina is able to detect Anders' real signal to the east of the UNSC position.
Red Team's Warthog is moving at high speed, with its turret firing at enemies around it.
The Warthog drives over a small hill and crashes, forcing the Spartans to continue on foot. Countless Flood structures and forms stands in front of them.
After 10 minutes:
The UNSC forces advance to Red Team's position, encountering and destroying the first Flood colony.
All five locations of the Flood colonies are shown on the minimap. The second Flood colony is destroyed.
After some time, however, one of the destroyed Flood colonies has regenerated.
The UNSC forces move near Red Team.
The UNSC forces assault the Proto-Gravemind, killing it.
The Proto-Gravemind collapses as the liquid inside spills out.