It took a lot of work, but we're finally ready to get out of this awful asylum.
First things first - stick to the master plan, and get a vehicle.
Unlike normal walkthroughs, in Nice Game Hints you can select just the puzzle you want hints for. Here are listed the puzzles for "After acquiring the master key" in Edna & Harvey: The Breakout. The guide you choose only contains information about that puzzle, reducing possible spoilers for other puzzles.