As the chapter starts, get out of the torpedo with your knife ready. Prepare to be crouched and stealth throughout most of this chapter to avoid Commanders from sounding the alarm. In fact, your Signal Detected monitor should come up almost right away. Carefully move forward and eliminate the two guards on the ground level. One of them will walk right past you, making for an easy kill. Then go up the stairs to the next level, careful not to let anyone spot you. Stealthily taking out the two guards and Commander in this area can be tricky, but memorize the timing and strike fast, and things should work out. Once they're taken care of, make your way to the door. There's a map on the right wall just as you step through. Take it and continue moving to the next door.
Get ready for a heavy fight, and don't be stingy with the Hand Grenades. Toss them and keep moving from room to room to replenish your health, ammo, and armor. Meanwhile, the trusty Automatic Shotgun should make short work of most of the Nazis. If you're not on the ground level, head back there. There you'll find an open door with more soldiers on the other side. Toss in a couple Hand Grenades to clear them out and walk through. Use the Laserkraftwerk to cut all the chains, then hook up the radio on the desk to complete this section. Follow Fergus and Set without fear of being attacked. Do whatever they say until you reach the secret vault, then run across the bridge and prepare to go up to the top. Use the Laserkraftwerk on the magnetic spheres, which turns them into steps. Move quickly, because they disappear after a short while. Keep moving and shooting until you reach the summit, then lower and raise the platform according to instructions in order to finish the chapter. Congratulations! You've reached the top!