Assault on the Control Room is the fifth level of Halo: Combat Evolved and was a major conflict within the Battle of Installation 04. Master Chief and Cortana traveled in Echo 419 to a canyon via a maze of underground tunnels. After a lot of fighting, he reached the Control Room. Upon his entrance, he placed Cortana into the Control room's mainframe. He was then ordered by Cortana to stop Keyes from reaching a building Keyes believed to be a weapons cache. He quickly heads back for Echo 419, leaving Cortana in the mainframe.