1F: The Bathroom
When you return to the Mansion, walk up to the glowing door in the Foyer. It will start to flash, and the spikes will disappear, opening the door to Area 2. Walk up and unlock it. If you check your map, you'll see that the only open door in this corridor is in the north-west. Go there. You can ignore the yellow Bowlers and Purple Bombers you meet along the way, since they are the weakest of ghosts you will meet (other than mice and bats, also found here). This room contains two new ghosts, Grabbers, who grab Luigi to impede his movement. This particular variety can't harm Luigi, but later types of this ghost can. If they grab you, tilt 
left and right several times to shake them off. Catch them to turn on the lights. You'll receive a call from the Professor. He'll explain Grabber ghosts. Once he finishes talking, you'll notice that the key is on a shelf. Suck it down with the vacuum. Head for the next room.
1F: The Ballroom
In this room, there is some cheerful music playing. There are also some new ghosts, Shy-Guys, dancing in pairs. To defeat these, suck off their masks to expose their hearts, then stun them and catch them as normal. Try to catch both members of a pair at once, since any left alone will try to attack you. Once you have caught the three pairs, the music will change, the checkered panels will begin to rotate, and the Portrait Ghosts, the Floating Whirlindas, will appear.
Their weakness is difficult to find. You must be on the same rotating panel as them to see them, then wait for them to twirl. This will reveal their heart in their moment of separation (despite there being two of them, they share a heart, unlike later grouped Portrait Ghosts). Catch them to turn on the lights and reveal the key to the next room, which is right next to this.
1F: The Storage Room
This room may seem small at first, but it won't be so for much longer. This room contains two Purple Punchers, two Red Grabbers, which can damage Luigi if they grab him, and a valuable Speedy Spirit, hidden in the boxes, which you should concentrate on first. Once the four main ghosts are caught, the lights will come on, but nothing else happens. Look in the mirror. You'll see a switch. If you look at it with your Game Boy Horror, you'll see it says 'Don't Push!' However, you should push it. Do so, and the entire left wall of the room will move back, revealing a new part of the room. Down here, a poster on the wall reads Danger!!. Remove it with your vacuum to reveal another switch. Push it to open the trap door, and release... the Boos, and their leader, King Boo! King Boo sees the Poltergust 3000 on Luigi's back, and all flee to various rooms throughout the Mansion. Once this fiasco is over, you'll receive a call from the Professor, who tells you that the Boos released the Portrait Ghosts, and invites you back to the Lab.
The Boo Radar
The Professor thinks that the Boos have captured Mario. He says that Boos grow stronger in numbers, and that their combined power must have been too much for Mario. To save Mario, you must now catch each Boo to weaken their power. To help find them, the Game Boy Horror has a secret function: the Boo Radar. It will flash red if a Boo is close to you, and yellow if there is a Boo in the room.
Now, return to the Mansion. Save with the Toad in the Foyer. You can now go back to every room you've completed previously, and capture the Boos hiding in them. There are fifty Boos in total, and they only hide in rooms you have completed, excluding minor rooms like balconies and bathrooms. Unlike other ghosts, Boos do not attract the pull of the Poltergust as they move, so you must also use 
to keep your vacuum pointing at them. They also have various levels of health, up to 300hp, and individual names. You will receive a call from the Professor, who will allow you to save, every time you catch one. Sometimes, he will have a piece of information about Boos. Once you've checked every room you've completed earlier, you should have eight Boos. After your fifth Boo, the Professor will advise you to go to the Washroom, which is beside the Bathroom on the first floor.
1F: The Washroom
This small room has a Toad, sitting, crying beside the toilet. Speak to him. 'I dropped a really important thing into the toilet...' Tell him, 'Don't worry about it!' He'll cheer up, and turn on the lights. Check the toilet to find a key. It opens a room in the south-east of the floor.
1F: The Fortune-Teller's Room
Shine your flashlight on the crystal ball on the table. It will begin to glow, until a Portrait Ghost appears in the chair. This is Madame Clairvoya, and is the only Portrait Ghost who will help you in your quest. She calls herself the 'Seer of dropped items', who can make predictions based on other peoples' lost possessions. You'll come back to her with items later, so go into the next room for now.
1F: The Mirror Room
This room has a large mirror on the back wall. As soon as you enter, the door will be covered in spikes. This room contains invisible Grabbers, whose locations can only be seen by their reflections, or the dust risen at the moment of their appearance. They cause Luigi to lose health if they grab him. You must catch all six of these to turn on the lights, and reveal a chest. Open it to find the Fire Element Medal, and receive a call from the Professor, who tells you about them. (See the sidebar for more details.) Walk up to the fire to find a Fire Element Ghost, and catch it to fill your vacuum with the Fire Element. You can expel the Element by pressing 
. Use it to light the two sets of candles, and open the door. Catch the Boo, and go back to the previous room.
Light the four sets of candles here to find a key on top of the front-right pillar. Vacuum it down, and go out into the corridor. Near the Washroom, there is a candlebra floating around. Light it up. A Portrait Ghost will appear, and start screaming, and run to the room you found the key for. Follow him there.
1F: The Laundry Room
The door on the back wall here is fake. You can either avoid it, or burn it off with the Fire Element. This room contains two Purple Punchers, one White Grabber, one Red Grabber, and a Boo. The green chest that appears is full of cash. Check the washing machine to find... Mario's Hat! This is one of the items you need to find and bring to Madame Clairvoya. There are four more, all Mario's items. Now go to the next room, through the front door.
1F: The Butler's Room
If you were too long in the previous room, the Portrait Ghost, Shivers, the Butler, will have returned to his post in the corridor, in which case you'll need to go back out and light his candles again. Once he's there, he will sit down on the stool and get burnt by the candles. Catch him now, avoiding the mice. A chest will appear, containing a key. Catch the Boo. But before you leave, look in the back-right corner with your Game Boy Horror. You'll see a mouse-hole here. Scan it to start a vacuum, that will pull you in.
1F: The Hidden Room
This room is full of Bats... and treasure chests! But not all contain money, some contain ghosts. Those that hold ghosts are:
- Small chest, front-right
- Large chest, middle
- Large chest, left
- Small chest, back-left
All ghosts are Icy Punchers, whose hearts must be melted before you can stun them. If you need some Fire Element, some of the candles in the corridor have Fire Element Ghosts. Once all are caught, a green money chest will appear. This chest contains your first gems, which are extremely valuable. Almost everything that moves in this room contains money, even the chandelier. Catch the Boo, and, once you've cleaned out the room, scan the mouse-hole in the back-left corner to escape.