GLOOMY MANOR A-3
Welcome to Gloomy Manor A-3, Quiet Please! If you've been following our guide, there are 3 potential Gem Stones here that you haven't found yet, and one Boo that you'll have to come back later for once you have the Dark Light And there's actually a gem in the very first room.
Interact with the knight on the right to knock his helmet loose. then grab it and aim upward toward a painting on the left side of the back wall. Launch the helmet at it to knock it loose, revealing the mansion's 5th gem. Now head North to the foyer.
Now before we proceed with the mission, you should know that this mission's Boo is nearby, though you won't be able to expose him until after you find the Dark Light device in Gloomy Manor's 4th mission. Once you have it, you'll want to head through the Common Hall and into the Studio. Once there, you'll see a sheet seemingly suspended in air. Suck it up with your vacuum, then shine the Dark Light on the empty space to reveal a hidden canvas where the Boo's hiding. Now just suck up the spirit balls to force him to show himself.
Regardless, back in the foyeur, use the crank Professor E. Gadd gave you on the machine along the back wall. This will lower the aquarium, revealing a door on the floor above. Take the stairs and head on through into the lobby. After you take down the two greenies, the elevator will begin to move on its way to your floor-- get ready to unleash a flash of your flashlight as soon as it arrives to easily take down the spiders and stun the ghost riding it in one fell swoop. Once clear, exit out the northern door into the library. If you don't care about collecting cash from the gold spiders or mice, then it's best to hurry along the walkway to the door on the opposite side to avoid taking damage from the flying books. It leads into the dining room. Head to the far side to find one of E. Gadd's sensors along the ceiling that you can flash with your flashlight to reveal the mansion's 6th gem. Now use your vacuum to pull the nearby tassel in the corner to open the dumbwaiter. Hop inside to ride it down to the kitchen.
Only the western door is unlocked here, but if you try and exit through it, some ghosts will appear --some of which are decked out in kitchen utensils, which shield them from your strobe light. Wait for them to attack, then flash them when their guard is down. Once clear, don't exit yet. Instead, open the fridge. Inside, you'll find the mansion's 7th gem--but it's encased in a block of ice! Simply melt it over the oven's open flame to add it to your collection. Now exit through the western door, into the lower floor of the library.
Here, you'll meet the Poltergeist. He's actually not that tough, with the only tricky part being actually tracking him down since he's invisible most of the time. Keep a close eye on the books for clues as to where he might be. And if you see a book being raised, get ready to dodge out of the way, or quickly flash him, to make him drop it. Once you've taken him down, two more will appear, but they're really not much tougher. Once you've sucked them up, the mission will be over.