“Nightbitch” is a very compelling dark comedy about the challenges that are inherent to child-rearing, but it is unfortunately saddled with a ridiculous metaphor at its center that drags the pacing to a halt. There may have been a way to spin “Nighbitch” into a more absurdist romp that embraced visceral horror, and it also may have succeeded had it leaned entirely into the drama with an approach that felt more authentic. Unfortunately, “Nighbitch” feels lost somewhere in the middle, leading to a rather unpleasant slog that lacks cohesiveness. While it would be hard to fault the ambition behind its concept, “Nighbitch” is not nearly as shocking, devastating, or funny as it is clearly aiming to be.

Based on the novel of the same name by Rachel Yoder, “Nighbitch” centers on an unnamed mother (Amy Adams) who finds it harder to raise her son (played by twin child actors Arleigh...