We don’t get many horror movies with better performances than the ones Lupita Nyong’o and Elisabeth Moss give in “Us.”

The latest from writer/director Jordan Peele is not as assured or concise as his “Get Out,” but it’s more frightening, and a lot of that has to do with those two women. Nyong’o is the capital-letter Star of the movie in two roles: Adelaide is a good-humored wife and mother of two whose well-off family has just begun a stay in their weekend home. And Red is the leader of another family, each of whose members looks just like Adelaide’s, who crash the holiday and almost immediately begin wreaking violent havoc.

Who are they: Aliens? A cult? The devil’s minions? (With its demonic choruses, the soundtrack has fun with that last idea.)

No surprise: The answer is closer to home. As with “Get Out,” Peele exploits the sorts of everyday fears that we manage to keep in our subconscious most of the time. This time it’s the feeling that if someone wanted to break into our homes, they probably could, and that we aren’t sure we’re capable of defending the ones we love in extreme situations.

We don’t know much about the dynamic of Adelaide’s family before the violence starts, but, once it does, it becomes clear that she is the one in the family who instinctively knows what to do. As portrayed by Nyong’o, Adelaide is a formidable, intelligent woman. And she must do battle with a woman who looks like her and is just as formidable and intelligent. Nyong’o delivers Red’s lines hoarsely and blankly, as if she hates being bothered to describe the awful things she plans to do.

Moss’ role, as a neighbor named Kitty, is much smaller, but it embodies the hilarious-then-terrifying-then-hilarious-again vibe that drives “Us.” When Kitty’s home is about to be invaded, Moss has a line that wouldn’t have seemed funny on the page — she’s just sending her kids off to bed — but her contemptuous, extremely non-mom-like delivery of it gets the biggest laugh in the film. Our laughter is brought up short, though, when, our guard down, we are blasted with a moment that is shocking specifically because of Moss’ surprising and original reading of that line.

As long as Peele is coasting on a wave of tantalizing unease, this feels like it could be a new classic, in a small company with “Let the Right One In,” the 2004 “Dawn of the Dead” remake and a few others. But then Peele feels the need to explain everything.

The movie works best when we’re not sure what’s going on, other than that humans have failed in their responsibility to take care of one another, and that Red and her ilk have come to make us pay for it. (The obvious antecedent is cartoonist Walt Kelly’s oft-quoted “We have met the enemy and he is us.”) In the final 45 minutes, which really should be only 15 minutes, Peele commits the disappointing error of having a character spell out exactly what’s going on and breaking the movie’s spell.

Peele gets back in the creepy column with the final scene, which returns us to the beginning of the movie and reiterates a paranoid worry that lurks in the background of every moment of “Us”: If you’re trying to do away with people who look exactly like you, how can you be sure you’re the good guy?