Go back to the narrow passage and through this door. Deal first with the two sub mutants.

Use your plasma gun to hit these enemies around the corner. The Super Officer will leave you a missile launcher. Collect what health you need.

Fight the enemies in this room, including the armour by the locked (silver) door to the north. Collect more health and find three extra missiles. Beware the bomb in front of the door to the left.

Make your way over here again. Go north past the water puddle. Bring down the sub mutants ahead.

Enter the library past the death chalice. Find revolver ammo right within to the left. Switch quickly between the revolver and the axe while fighting the guards and the ghosts. Don't get surprised by anyone hiding among the book shelves. Get the health chalices.

Find the silver key in this secret part of the library.

Continue.