|Location||Taking the door labeled "Escape" prior to the Mind Control Facility.|
The Museum Ending is the ending that occurs when you arrive at the Mind Control Facility, but instead entering it, you go to the hallway with "Escape" written on it.
Obtaining The Ending
Exit Stanley's Office. At the 2 doors, pick the one on the left. Once you get to the staircase, go up to the boss's office, and to the Mind Control Facility. But instead of entering the room, turn left and follow the "Escape" sign. The narrator will comment on how you can turn back at any point in time. You'll fall into a metal jaws trap at the end of the hallway.
Right before the metal jaws crush you, they will suddenly stop. A Female Narrator will narrate the story, mocking the original narration by saying "Stanley was already dead from the moment he hit start". The cart beneath Stanley opens and Stanley will fall onto a catwalk. Walk past the jaws and Stanley will enter a white Museum detailing the development of The Stanley Parable game, including its beta versions. Go to the back section of the museum and you'll see a banner of "The Stanley Parable", along with an "on/off" lever. The female narrator then laughs, stating that although "these two" (referring to the Narrator and Stanley) wish to destroy one another, they actually need each other. When you touch the lever, Stanley will be transported back to the moving metal jaws trap. The Female Narrator will urgently tell the player to hit the escape button and press "quit". Failure to do so will cause Stanley's death.