King Boo frames a vacuum job in Luigi's Mansion, the GameCube launch game in which Luigi tours a locked house room by room. Professor E. Gadd's Poltergust 3000 sucks portrait ghosts in once the flashlight has stunned them, and the 2001 mansion started the series.
Keys, elements, and a ghost's joke tell you which room is next. Boolossus and the gallery of painted spirits are the bosses, and Mario is the reason Luigi walked through the door, not the hero holding the nozzle.
Later numbered games are sequels set in other places, not this same foyer. The launch disc is the original house, the vacuum, and King Boo's portrait trick.
E. Gadd's lab in the basement is where the captured ghosts go. Anyone who starts the series elsewhere is visiting a follow-up; the flashlight tour begins here.