Take the stairs up right away; use the chest to get inside. You will enter the room of the creature that will soon be relentlessly tailing you. Get onto the toilet, then the sink and then climb the cabinet. Jump onto the table with the key - drop the key onto the floor and jump down.
Approach the slide wall on the right and push. Take the key, go towards the lock and throw it (Six can't jump while holding an item). Go with the key towards the lock and open it.
Take the teaddybear and approach the button with it. Hold the "throw" key for a while, and throw the bear at the button to call the elevator. Grab the teddy again and repeat this trick inside the elevator so it takes you down.
Exit and run to the left. Six will have another spasm of hunger. Continue left till you reach a peace of raw meat in the cage - eat it... and you'll be trapped.