It's the Invisible Lorenzo Glitch, but be warned, somethings will go wrong, but not so much that you'll have to restart your game from the beginning:

When you first enter the House of Truth, go into the long corridor (Lorenzo's room is straight ahead at the end of it). Retrieve the candlestick like you would normally do, but instead of going through Lorenzo's door, kick open the red vase and free the Luminescence inside. DO NOT LET IT HIT FIONA. Lead it down to the area with Fiona lights the candle stick and the scene where Fiona throws it into the flammable boxes will take place. . .Without Lorenzo in it.

You'll be able to continue to the area where Old Lorenzo's boss fight takes place, again, all scenes will occur without Lorenzo and he won't pursue you, YOU WON'T EVEN HAVE TO DO THE BOSS FIGHT.

Because there is no boss fight, you don't need the key Lorenzo leaves behind, just go through the door.

When you are locked in the room, and Lorenzo Youth commences speaking to you, things will kind of get glitchy. For instance: After the Lorenzo Youth is ready to let you out, if you do not exit the room after a period of time Lorenzo Youth actually enters the room and pursues you just as any stalker would.

All you have to do is enter the room where Lorenzo becomes his Youth form and he'll start pursuing you like usual, I don't remember anything else glitching after this, it's pretty much back to normal once you've watched the "Return to Youth" cutscene.

Glad to have shared this with you all, hope you get as much of a kick out of it as me!!

Thanks for sharing! I tried and I noticed three other things:

1. If you go to the room where you normally meets Lorenzo(instead of going straight to the boss-fight-room) he will appear and everything goes on as usual.

2. It may have been a coincidence, but I think not. When Fiona entered the place where you first hear young Lorenzo's vioce, Hewie entered with her. That has never happened to me before and I've finished this game 6 times.

3. The y.Lorenzo chase music was the same as Riccardo's.

quote precioushewie

Thanks for sharing! I tried and I noticed three other things:

1. If you go to the room where you normally meets Lorenzo(instead of going straight to the boss-fight-room) he will appear and everything goes on as usual.

2. It may have been a coincidence, but I think not. When Fiona entered the place where you first hear young Lorenzo's vioce, Hewie entered with her. That has never happened to me before and I've finished this game 6 times.

3. The y.Lorenzo chase music was the same as Riccardo's.

I've done this before. Every time I do, Hewie's always stuck in that door.