Search for Black Rock Processing
You need to get back down to the Maintenance Sector, so head back to the main elevator south of Central Research. Take the first door on your left toward Black Rock Processing and take out the few enemies that spawn, including a Hiss Cluster. Go past the Security Check and rather than following the signs to Black Rock Processing, take the left door toward the Turbine Room instead.
Pull the power supply out of the socket on the left wall then jump over the now-inoperable turbines, but bring a power supply with you to the top. Insert that one and the other one up there into the sockets in order to open the door, then stand at the edge of the walkway and pull the cord three times to go back to the Oceanview Motel.
Walk toward the end and head into the second open door. There's four things to interact with here: a chair, radio, painting, and plant pot, pictured above. You need to mirror the other room, so leave the chair pulled out, straighten up the painting, put the radio on the right, and the plant pot on the left. Go into the final room at the end to pick up the key that has now appeared, then use it on the door near the cord at the other end. Pull the cord in the room three times to be teleported back.
Head back down to the walkway by following the signs for Black Rock Processing, then cross the bridge, go up the stairs, to the right, and drop down into the office. You'll be able to hear some gunshots so go up the stairs, kill all the enemies, and cleanse the next control point. Then head up the stairs to speak to Arish, the friendly fellow you met earlier near the Power Plant.
Find a Black Rock Prism
The next section is fairly linear, so keep following the corridors until you go through the double doors into the open warehouse area. Interact with the red box on the right-hand side of the room and a Black Rock Prism will spawn. It teleports away frequently and completely vanishes, so just shoot it when you can and Launch debris at it whenever possible to take it down. When it's dead, go through the door marked LAB 01.
Find the Black Rock Quarry
Now you need to find the Black Rock Quarry. Pick up the Security Clearance Level 5 and go through the door and into the service elevator. At the top, kill the enemies on the walkway and keep following the signs for Black Rock Quarry. Eventually you'll be back at the NSC Power Plant, but much higher up. Claim the Control Point and eliminate the enemies up there as you cross to the other side.
Go through the next Level 5 security door, then start dropping down ledge by ledge as you discover the elevator is broken. Watch out for the couple of Hiss Charged laying in wait as you clamber down. When you get to the bottom, cleanse the Control Point then walk out towards Black Rock Quarry, where enemies will spawn.
Take the first right turn when you've cleared out all the enemies, then opt for the path that goes above the Astral Entity and hop over the floating rocks. Now you're in Black Rock Quarry.
Activate the explosives to excavate the Black Rock Prism
On one side of the quarry is a bunch of explosives stuck to a wall, with three power sockets around it. Grab three power supplies and stick them in the wall with Launch, then deal with the surrounding enemies before interacting with the terminal in the middle of the quarry.
This will trigger the explosion so you can collect some Black Rock, then hightail it out of there as some more Astral Entities will spawn and chase you. Go back to the Control Point then fast travel to Central Executive to speak with Marshall.
Main Missions:
Control walkthrough: Welcome to the Oldest House
Control walkthrough: Unknown Caller
Control walkthrough: Directorial Override
Control walkthrough: Old Boys' Club
Control walkthrough: Threshold
Control walkthrough: My Brother's Keeper
Control walkthrough: The Face of the Enemy
Control walkthrough: Finnish Tango
Control walkthrough: Polaris
Control walkthrough: Take Control
Side Missions:
Control walkthrough: Old Friends
Control walkthrough: Fridge Duty
Control walkthrough: Self-Reflection
Control walkthrough: Mr Tommasi
Control walkthrough: Old Growth
Control walkthrough: A Matter of Time
Control walkthrough: Langston's Runaways
Control walkthrough: The Enemy Within
Control walkthrough: Mold Removal
Control walkthrough: What a Mess (all missions)
