You searched the house and found 8 pieces of painting. But then Slenderman knocked you out. You now know the secret of Slendrina, and you can't leave the house... If you want to leave this place alive, you will need to find 8 books. Good luck in Slenderina Must Die: The Cellar Room.
Use WASD to walk around, mouse to look around. Left mouse button to fire, right mouse button to aim. Mouse wheel to change weapons. R to reload, F to pick up items, left shift to run, left CTRL to crouch, C to prone and space to jump.