I've just entered the area near the beginning where the stairs collapse and you need to fix a few machines. I noticed that there were two fuses, so I grabbed the second one as I left the room, figuring I would need it later. After activating the second machine, I went through the door it opened with the fuse, then set it down on some barrels to get it out of my vision. I continued up to the third machine, noticed that yes, the fuse was blown... but there was a tremor and the door back was closed. I figured no problem, I'll just go through that barred door I saw earlier, run up to the barrels, and grab my fuse and run all the way back (so much for saving time!)... but the door leading to that area from the first machine also closed. I have no way that I can see to get to the fuse I set down.

Am I well and truly stuck and need to restart the game, or am I missing something?

Thank you! I finally found one near the door that lead to the area (silly me was only looking in 'the fuse room'). You saved me from playing the mansion intro for a third time, heh.

Funnily enough, the collapsed area that the third machine's door lead to... is where I left the fuse. So, now I'm carrying it with again just in case.