Start the level "Mansion" and walk trough the first door. Go upstairs towards the next door where you have to push a red button to open it. Dont do that!! When you stand in front of that door turn left where you see the statue and the exit of the game. Now lift both of your hands up and run towards the egde. Jump at the right moment and grab the ledge on the other side and pull yourself up. Maybe you need a few tries I recommend to look up while you are running so the hands are in the highest position.