Inferno (1978)

One thing is certain about the great Italian horror maestro Dario Argento, you can always count on his style if not his substance -- his films are great to look at but could do with a logic transplant. "Inferno" follows "Suspiria" as the second part of a proposed trilogy (the third has never been made) about possessed buildings in three different cities (here supposedly New York -- as shot in a roman studio) that house the three mothers or the three gates to hell or somesuch.  Lots of deaths and artistic gore but don't for goodness sake ask whodunnit.