Part 2: Science Lab

Follow the corridors until you enter a lengthy hallway with a ramp leading down. Kill the pair of regulars and the flamer at the bottom of the ramp.

Note the glowing yellow tanks in this room. They contain zombie-like enemies who will attack you if you break any of the cases. Take care not to disturb them.

Exit the door into the hallway at the end and turn left. You can use the weapon machine here if you wish.

Enter the door at the end of the hallway to continue.

Immediately turn right and kill the guy looking at the test tube with a takedown (a stealthy kill performed from behind).

Crouch and continue along the wall to kill the next guy ahead in the same way.

Move forward a little further, keeping an eye out for a short set of stairs on the left. Climb up here, takedown the guard patrolling here and disable the alarm (a device that alerts enemies).

Take out the rest of the enemies in the room.

At the back of the room, you will find a set of stairs leading to the top of the room.

At the top, approach the objective marker (a visual indicator on your screen showing your goal). As you do, a timer will appear at the top of the screen.

Defend yourself against an oncoming horde of enemies until the timer runs out. The majority will be regulars and chargers, but you are liable to see a heavy flamer or two as well.

When the timer is up, the door with the objective marker will open, so run through it.

Follow the hallway to the end and kill the lone regular in here.

Head down the stairs at the back of the room.

Make your way through the various corridors towards the objective marker.

When you reach the next large lab room, use the d20 (a specific item or mechanic) to lure the enemies on the bottom over to the left side of the room.

Quickly sneak over to the small tunnel halfway across the room on the right and disable the alarm.

Take out the enemies here.

Once you have cleared the lower level, another 2-3 regulars, a heavy flamer, and a molotox enemy (a type of enemy) will appear.

Afterwards, once you head upstairs, you will have to fight through 10-12 regulars and a heavy flamer to reach the exit door.

Enter the door and kill the molotox enemies at the end.

Continue down the stairs and kill one final heavy flamer in the area there.