After watching Helen's movie, go to the far right of the room to remove the plate and put Gooigi in the ventilation hatch. Climb with the hose, once again on the right. Once at the top, hang Gooigi on the rope and then fall into the void with it to pull the screen.
The idea behind the floor is as follows: 4 rooms with 4 puzzles and 4 keys to reach the Hellen Gravely boss's room. Let's start with the one on the far right, you'll have to make the door appear to the Dark-Light Device.
In this lounge, tak Gooigi to the back of the room, then rotate the center of the room with your vacuum, 3 or 4 times, until a lever is accessible. This will disable the lasers: turn it all over again and go get your first key. Be careful, when you leave, mummies will attack you, if you don't remember the technique: ZL+ZR, suck the cloth once they are on the ground and pull.
Now we go to the room on the far left.
A ghost with two tongues will try to swallow you, take Gooigi out and tear him to pieces. Enter the room and, straight away, take a ZL+ZR jump to reveal all the lasers. After that, it's just a matter of timing. We can't really help you with that, so good luck!
Go down to the bottom landing to reach the switch that deactivates the lasers in the room, then go up to get the key.
Go to the northern part of the main room, with a Dark-Light Device shot on the wall in front of you. In this rather cosy room, shoot a suction cup on the right dummy to transform the room into a hellish pendulum.
The goal is to counterbalance, but not too much, to go up to the right first and turn off the lasers. Then, go to the left and catch the key. Be careful, do not lean too quickly otherwise you will fall into the abyss and lose 10 points of life.
Reveal the wall of the central corridor of the northern part of the room with the Dark-Light Device in order to have access to a last room full of lasers.
Do a litlle ZL+ZR to reveal them and like in the second room, we will have to have the right timing to jump over them at the right time. Deactivate the obstacles with the lever once you have almost finished walking around the bathroom, then turn the tap on the bathtub to remove the key.
On leaving, yet another fight will take place and the camera will pass in top view to let you anticipate a laser. Once all the ghosts have been sucked in, put the 4 keys at the back of the room, and it's time to face Hellen!
Hellen Gravely, the one who set you up and handed over your friends to King Boo is now standing in front of you. For this fight, several things to take into account, here is what you need to know:
- The central pillar will ultimately be your main enemy: when there is only one laser down there, just get ready to jump, when there are 3 lasers, get as close as you can to the pillar so that it doesn't catch up with you when it starts to turn at full speed.
- When the pillar swings 4 rays of color, it means that Gooigi will have to turn them off at the bottom, for one simple reason: Hellen will struggle and make you move all over the place when you catch her with the Poltergust. Pass Gooigi through one of the holes, and turn off the switches by moving the panels to clear a path for you. Warning: the pink and orange switches must be pulled with a suction cup, while the other two can be simply pressed on X.
- When she runs out of life points, Hellen will be more aggressive and you will have to constantly switch between Gooigi and Luigi. Moreover, a stream will pass down, capable of eliminating Gooigi in one hit. The best way here is still to ask a player 2 to come and join the fight as it's one of the most difficult phases of the game.
- Hellen can be flashed, like many bosses, after a charged attack that will keep her on the ground. As mentioned above, make sure that all 4 colored lasers are disabled.
Finally take a good look at the walls of the room, as soon as a green light is on it means that she can be flashed for a little health, it never hurts.
After the fight, finally free your brother from his painting. The end is near!