From Halopedia, the Halo wiki
Infinity science personnel request a Spartan Fireteam to investigate a Forerunner structure located within Requiem's jungle. Commander Palmer, impressed from their previous mission, sends Fireteam Crimson to scout out the area. Crimson enters a large atrium inside the structure and encounter no hostiles. The place is seemingly abandoned until Jared Miller, Crimsons mission handler, picks up power fluctuations coming from the back-end of the facility. Crimson proceeds to the power source and encounters Promethean Crawlers guarding a star chart. They are ordered to extract the data from a nearby console. As Miller establishes an up-link to extract the data, Crimson fend off multiple Crawlers who translocate near them. With the data pulled, Palmer orders Crimson to pull-back and await for extraction. As Crimson leaves, they run into a group of Promethean Knights.
The situation goes awry when the structure's main entrance is closed and more Promethean forces show up. Crimson is forced to defend themselves. Miller finds a way for the Spartans to escape, and points them to a console that controls the facility's door. Crimson activates the controls and are ordered to clear out any remaining hostiles. With the structure secured and the data uploaded, the mission is a success. Spartan Robert Dalton arrives with a Pelican dropship for extraction.
All dialogue is spoken through the COM.
The camera pans through the Refuge, finally focusing on a star map at the far end of the map.
A waypoint appears at the rear of the facility. As a player draws close several Crawlers appear and open fire on Crimson.
Crimson reaches the waypoint set on the star map.
The player accesses the switch.
More Crawlers appear.
A waypoint appears at the far end of the facility.
As Crimson makes its way down the hallway a Promethean Knight translocates and blocks their path.
As the player nears the facility's exit the doors suddenly close and another wave of Prometheans appear.
A waypoint appears on the player's HUD.
The player activates the switch.
Promethean Watchers appear
Crimson clears the area:
Fireteam Crimson exits the same way they arrived.