(On Cable TV, April 2018) There are stories that men tell each other in order to keep themselves in line. Don’t crush on crazy; don’t crawl inside the bottle; don’t run with criminals; don’t stray outside your marriage; don’t neglect your kids. Elementary life lessons, but worth repeating, often with maximal effect, in order to feel better about an ordinary life. When those morals are handled through genre methods, they become high-impact morality tales. Think Fatal Attraction. And if you give the story to a horror director like Eli Roth … well, you end up with something like Knock Knock, in which a good husband/dad finds himself powerless to resist the advances of two women when they show up at his doorstep when his wife and kids are away. What follows is a pair of steamy sex scenes. But what follows what follows is a merciless takedown of the man’s life using video and social media. The moral of the story here is clear enough: Destroy Facebook. Japes aside, does it work? Well, yes and no. Famously stoic Keanu Reeves is a curious choice as a good husband/dad, given that his innate reserve doesn’t really help him reach the emotional extremes required by the script. On the other hand, Ana de Armas and Lorenza Izzo are good picks as the ruthless temptresses—fortunately enough, since much of the Knock Knock’s credibility (or what passes for it given that it’s a quick-and-dirty exploitation film) depends on them—de Armas is particularly good, which explains why her career has taken off since then. Otherwise, though, the film does feel as if it doesn’t have enough depth to sustain its straightforward warning. It ends limply, in perhaps the tritest possible way. As a horror-erotic take on the home invasion genre, it sits uncomfortably between two very different genre—I wouldn’t be surprised if there was one (or fifteen) XXX-rated parodies focusing on the eroticism, and we’ve already seen an entire pure-horror home invasion subgenre come and go and come again. For Roth, who straddles the line between mainstream and extreme filmmaker, this is curiously tepid stuff—he’s obviously daring enough to feature two very explicit sex scenes, but the rest of the picture goes nowhere. As a result, Knock Knock doesn’t unnerve as much as it annoys, and that’s a fatal flaw in the kind of moral lesson it almost tries to be.