Miscounted, sorry. So I walk east to the button-and-platform room (#2). I go up. I walk east into the red-guy-below-me room (#3), and walk across it. I walk east into the red-guy-and-button-below-me room (#4) I walk east, the guy follows me and falls down onto the button, which opens the door. Cool.
Now I walk through that door, and...boom, screen wipes, and I'm back at the start.
If I screenshot really fast, I get the above image, if that helps.