Stuart Gordon has spent most of his cinematic career turning H.P. Lovecraft tales into perverse, creepy, and silly movies. And his "Dreams in the Witch House" episode of Masters of Horror is epic Lovecraft madness that crosses string theory with witch sex.
Like most of Gordon's work - except perhaps for Dagon - "Dreams" is a very loose interpretation of Lovecraft. In this adaptation, a graduate student at Miskatonic University (of course) is looking for a quiet apartment where he can complete his dissertation on string theory. He's figured out that by building special "non euclidean" shapes, two universes can intersect!
And that's just what happens in his weirdly-shaped apartment, where a witch and her human-faced rat come through the walls and force him to do their bloody bidding. Which seems mostly to involve slaughtering his neighbor's kid, whom he has been tricked into babysitting. But first, before the baby-killing, the witch gratuitously seduces him in the witchiest possible manner. And reveals why witch sex is always unsafe.
This is Lovecraft, so no, things do not end well. Unless you consider having your guts eaten out by a rat with a human face while you're locked up in a mental institution.