How to get the basement key in Blue Prince

Finding the basement key in Blue Prince is your gateway to completing its labyrinth of puzzles. As you work your way around the mansion, you'll find a number of items and keys you can use to progress further and unlock special rooms. But the basement key is arguably the most important. This key is the only way you'll be able to continue exploring and find the coveted room 46.

There's only one place the basement key can be found in Blue Prince, which makes it significantly easier than any...