This achievement is story-related and happens in the first sequence of Episode 8. You’ll have to destroy enough Roots of Evil to get fifty Spectral Vision. Once you’ve done that, head towards the waypoint at the eastern end of the map. There’s a force field around the building that you can only see when your eyes are closed. To bring down the force field, you have to throw a Molotov cocktail over it to burn down the huge tree that powers the barrier. There are handkerchiefs and several bottles of flammable liquid down the path, so you have some items to use.
Once the tree is burned, go through the door that it was blocking and look for the symbol on the right. Light it up to open up a hole in the floor. Shoot the ring at the top of the pole in the middle of the room to get a rope that you can use to climb down the hole. At the end of the rope, jump to the ledge on the left and shimmy around it to drop down on another ledge. Grab this rope, climb to the bottom, walk to the end of the hallway and you’ll trigger a cutscene and unlock the achievement.