I'm looking for a film I watched at home on TV when I was a kid, probably between 1976 and 1980. The film deals with a band of people settling in a big house, perhaps a mansion.
I remember a scene where one man, in his bedroom has the great surprise to see the girl he's secretly in love with, join him in bed. But at the second she's standing over him, she turns into mud that splash all over him and the bed. Terrified, he's helped by the others to have a shower to get rid of the mud.
Another scene I remember is that they're all standing at the floor level, and they hear what looks like foot steps coming from the upper floor, but appears to be a ball going down the stairs.