In this section of the guide to Layers of Fear 2, we describe the exploration of the basement in act 3. It's one of the rooms that has to be explored during the 3rd act of the game. The basement stage is quite short and only requires finding a few mannequin heads.
Just as before, you need to walk along the metal balcony above the hall with the projector. The key to the Basement will hang at the entrance to the ventilation shaft. Take the key, open the shaft and start making your way through it.
After you get back home, go down all the way (the arrows will show the way) and use the key to unlock the transitions to the basement.
Reach the head of the mannequin and start turning it to eventually unscrew it and add it to the inventory. Go to the big chest, open it, and throw the first head inside.
A new passage will materialize nearby. Use it to get to the other mannequin head. As before, unscrew it and move it to the drawer. Once again, use the newly opened passage. A little longer hike will lead you to the third head of the dummy. Take it with you and go back to the box. After unlocking the next passage, go get the last, fourth, head of the dummy. After returning to the box, hide inside it with the newfound head.
After resuming the game, open the box and remove the movie poster (A Wondrous Voyage) from it, as shown in the picture.
You can already get out of the basement and finish this rather short segment.