So, in the film, Eve Trawbridge and Bob Rainsford have gone into the trophy room, in which they find human heads on the wall, showing that Zaroff kills. The bad guy enters, so they hide, and Eve bumps into a large glass container, sloshing a head around. One of my students said at this point, "That must be a jarring experience." (I'm really going to get along with him.)
Also in the film, there is a character, Eve's brother, who is a silly, simple, drunken man. His role is to get shot by Zaroff, so we know that the heads aren't fake; the bad guy really is a psychopathic serial killer. As one of my classes was leaving, a student remarked, "And that is why it is important to be sober before you give consent."