Objective: Retrieve (3 reactor control units) and Repair (insert into reactor core).
You arrive in Troy Colony's power plant...
First, take out all the monsters in your neighbourhood, then read the comm terminal just before the large radiation door, which can be opened by walking up to it. Go south until you reach a door that takes you to a three-level elevator. Ride it one floor down to a room with a lava pit in the center and with a narrow stairway on one wall (you'll find the first reactor controller here). Up the stairs and to the left leads to the main control room with a comm term containing further instructions, as well as switch 1 and switch 2. Flip the first switch to raise the bridge into the main reactor chamber, and the second to open door B. Now, return to the upper level and head for the now opened door B, which leads to a room containing a 2x recharger and pattern buffer.
Go back to the elevator and ride it to the lowest floor. By now, bridge A will have lifted; if you cross into the main reactor chamber you'll find the other 2 reactor controllers and another terminal with clues on where to go next. Return to the outer ring, jump off the platform and enter the small service conduit. Follow it all the way to the end, then jump to the left at the lava pit. The small lift at the bottom will take you to a room with some carefully placed MiniHunters and some very small stairways, so watch your step...
Once you have opened the small door from the switch in the central pillar, jump down into the wider corridor. After getting rid of the aliens there, use the pattern buffer at the eastern end. Now head west to a room with plenty of lava. Carefully walk off the ledge onto the large platform, taking care not to end up in the lava. You'll need to get to switch 3a and switch 3b; each opens one half of door C. You'll need to keep door C open permanently to get inside, so flip each switch a second time once their respective door has opened; this will prevent them closing again. Now you can enter the room, which holds switch 4 and a recharger. This switch will lift ledge D, which in turn will grant you access to switch 5 around back. Trigger that with a grenade, and a ventilation duct (door E) to the north will now open.
Climb into the ventilation duct and follow it all the way to the main control room and switch 6, but watch out for exploding Boomers. Flip switch 6 to open the access hatch in the reactor core (door F), then follow the remainder of the ventilation duct (leading from just below the south wall to just outside the control room) until you're back at the three-level elevator. Ride it to the lowest floor again, and cross bridge A to the main reactor. Place the three reactor controllers, which you picked up along the way, in their appropriate places. This will allow you to leave by the nearby comm terminal, taking you to the next level, Citizen Cain...
