1. Zoom in on the cup. Get keys from behind it.
2. Turn around. Open the drawer and get the piece of paper from inside.
3. Turn to the clock an get the keys from behind it
Now you can open the safe on the floor. Get yet another set of keys.
4. Open the safe on the wall and grab the hammer.
5. Turn back to the cupboard with the drawer and smash it with the hammer by clicking on it (Note that the drawer must be closed for this to work). This will reveal the fourth set of keys
6. Click on the door of the cell to exit.

The End