"Morella," like "Berenice," partakes in Poe's creative break-though, as he began to articulate the very personal underpinnings of his dark genius. And yet, "Morella" is not quite as personal and daemonic as the earlier tale.
The story has been adapted to the cinema much more often than "Berenice," but to make the narrative work in a film, it's usually dumbed down into a story of a dead mother's spirit possessing the living body of her daughter, which isn't even close to what happens.
Whereas "Berenice" concerns a desired woman who seems to perish of a literal illness, "Morella" is about a woman who passes away because the unnamed narrator, her husband, mysteriously ceases to feel affection for her. Also in contrast to "Berenice," both the narrator and Morella seem to be ardent bookworms, schooled in abstruse philosophies like Fichte and Schelling. There may an element of envy in the narrator's indifference; perhaps he feels inferior to Morella's oft-described learning? In any case, though once again Poe's narrator disavows erotic feeling toward his beloved, this time he's somehow managed to father a child on Morella. A girl child is born just as Morella perishes, roughly repeating the trope in "Berenice" wherein narrator Egaeus is born when his mother dies.
The daughter grows to womanhood, and the narrator somehow manages to avoid giving her a name until she shows an almost identical resemblance to Morella. A christening-ritual requires the husband to name his daughter. He gives her the name "Morella" and she, like her mother. drops dead.
The story is preceded by a Platonic quote on the uniqueness of identity. Poe may be burlesquing this high-flown philosophy by showing the horror resulting when two entities share the same basic identity.