Main Objective: Reach Delta labs.
The monorail serves as transportation between the low level access sectors of the UAC complex and the priority access research facilities. Have all identification and security clearance data prepared for inspection.
Go to the right and pick up Sam Harding's PDA. Grab the supplies and use the health station if needed. Board the monorail and approach its controls. Activate the monorail then talk to T. Ryan when he appears. Reach the next monorail station.
Objective: Override Airlock. Manually override the monorail airlock systems.
Search the station for health and armor (there's more underneath the monorail track). Defeat some spiders then move through the door. Battle the soldier and a handful of guards. Search the corpses on the right for Gary Ross' PDA. The emails include the code for Junction 5, Site 2 airlock: 826.
Enter the wide transfer area. Watch around you constantly as guards, soldiers, and imps warp in. Search the shelves and corners for supplies then go up onto the opposite catwalk. At this point more imps and soldiers transport into the room. Ascend to the top. Approach the upper door and smash the soldier on the other side. Enter the control room. Grab Charles Hollies' PDA, which includes a cabinet code 142. Open the supply cabinet then use the computer to override the airlock. Input the code 826.
Retrace your steps back to the monorail and activate the controls. Proceed until the monorail crashes. Climb the ladder and shoot the soldier that approaches. You can grab some health down the path then return to the unlocked door. Kill the spiders in the hall (watch behind you too) and enter the next monorail section. Descend a ladder to go under the rail and find some ammo and supplies. Advance into the next hall and beware of several soldiers and imps that appear.
Open the next door and trigger a couple guards on the upper floor. Lure them into your shotgun blast. If one remains above, toss a grenade up there. Enter the security station at the top of the stairs and recover Karl Cullen's PDA. It includes info on the automated turrets and a cabinet code: 364.
Move into the door marked Delta Labs. When the imp appears, retreat and shoot the one that materialized behind you. Cross the bridge and shoot the soldier that enters from the front; turn around quickly to blast the imp.
At the security checkpoint, shoot the zombie ahead then scamper through the broken glass into the substation. Open the door behind you and find a couple storage cabinets. Open with the code 364. Allow the turrets to rip through the enemies that arrive. Deactivate the turrets once the enemies are dead and continue to the bay door to complete the level.