Continuity mistake: When the 1st chandelier fell, we see Peacock and White are standing near the front door. Scarlet then says "look!" Bringing everyone to look at the dead motorist in the study. Peacock and White are suddenly teleported to the study door behind Scarlet, even though they were quite far away with even a couple steps to climb down.
Revealing mistake: Just before the chandelier falls, Col. Mustard quite visibly flinches, even though, realistically, he would have no way of knowing that it was about to crash behind him.
Chosen answer: Tim Curry (as Wadsworth) states he knew about the secret passages because the house belongs to a friend of his. Tim Curry (as Mr. Boddy) says at the end of the movie that they "Could stack the bodies in the cellar and could all leave one by one." Which infers that Mr. Boddy has no intention of returning to the house. Either way, there is no definite way to tell who the house belongs to considering all the lying going on.
columbonet