The story here: I am in the process of cleaning out the basement. The door to the basement is in the floor in front of the laundry gear. We have it propped open to make it easier to get in and out (the door is pretty heavy; that ~45° board is hinged on the underside of the door, and there's a corresponding slot for it on the other side to securely hold it open).
So, Stranger, being the cat that he is, had to explore. He went into the basement, of course. Then he came up, and started exploring the edge of the open door. I just missed him attempting to go down the ~45° board, which is what made me get out the cam in the first place. However, you can see him thinking about jumping into the hole in the floor and onto the concrete steps leading to the basement in several shots in this clip. I'm glad he didn't try.