You know that feeling when you're reading a book and you think you’ve got it all figured out? You’re smug. You’ve spotted the red herrings. Then, Mary Kubica comes along and basically pulls the rug out from under your feet, leaving you staring at the pages in total disbelief.
That’s The Other Mrs. for you.
Honestly, even years after its 2020 release, people are still arguing about that ending. It’s one of those stories that lingers. It’s dark. It’s claustrophobic. And it deals with some heavy-duty themes that most "beach reads" wouldn't dare touch.
What Really Happens in The Other Mrs.?
The setup feels familiar at first, which is exactly how Kubica traps you. We meet Sadie and Will Foust. They’ve just uprooted their lives from the frantic energy of Chicago to move to a tiny, isolated island off the coast of Maine.
Why the move? Well, Will’s sister, Alice, died by suicide, leaving behind a creepy, crumbling house and a very troubled teenage daughter named Imogen.
Sadie is a doctor. She’s trying to be the "good wife" and the "good aunt," but everything feels off. The house smells like damp earth and old secrets. Then, just days after they arrive, their neighbor Morgan Baines is found brutally murdered.
The island is small. Everyone knows everyone. Suddenly, the newcomers are under a microscope.
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A Narrative That’s Intentionally Messy
Kubica doesn’t just give us Sadie’s perspective. That would be too easy. Instead, she weaves in these other voices that make you feel like you’re losing your mind right along with the characters.
- Camille: A woman who claims to be having an affair with Will. She’s bold, sensual, and honestly, kind of terrifying. She’s the "other woman" watching from the shadows.
- Mouse: A little girl living through a nightmare of abuse. Her chapters are short, cryptic, and heartbreaking.
- Sadie: Our primary narrator, who is increasingly dealing with "lost time" and memory gaps.
You spend half the book trying to figure out how these people are connected. Is Camille the woman Will cheated on Sadie with back in Chicago? Is Mouse a flashback to Imogen’s childhood? The way the pieces finally click together is where the real genius—and the real controversy—lies.
The Twist Everyone Is Talking About
Let’s get into the weeds. If you haven't read the book yet, look away. Major spoilers ahead.
The big reveal in The Other Mrs. is that Sadie, Camille, and Mouse are all the same person. Sadie is living with Dissociative Identity Disorder (DID). Camille is an "alter" that formed to handle the adult trauma and the "dirty work," while Mouse is the persona of her childhood self, trapped in the memory of her own abuse.
It turns out Sadie (as Camille) killed Morgan Baines. But she wasn't just a random killer. She was being manipulated by her husband, Will.
Will is the true villain here. He’s a serial gaslighter and a literal murderer who killed his fiancée, Erin, years ago. He realized Sadie had DID and used it to his advantage, "programming" Camille to eliminate people who threatened his secrets. He even swapped Sadie’s actual medication for placebos to make sure she stayed unstable and easy to control.
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Why Some Readers Felt Let Down
The use of DID as a plot twist is polarizing. Some critics argue it’s a bit of a "cheap" trope in psychological thrillers, often stigmatizing a real and complex mental health condition.
Others think the clues were there all along. For instance, when Sadie’s son Otto tells his teacher his mom gave him a knife for protection, and Sadie has no memory of it? That was Camille. When people claim they saw Sadie talking to Morgan, but she doesn't remember meeting her? Camille again.
It’s a "love it or hate it" ending. But you can't deny it's effective. The sheer malice of Will Foust makes your skin crawl. He didn't just hurt people; he hollowed out his wife’s mind and used the pieces as weapons.
The Setting as a Character
Maine in the winter is a classic thriller trope for a reason. It’s bleak.
The island setting in The Other Mrs. adds this layer of "nowhere to run" energy. Sadie is a city person. She’s used to the anonymity of Chicago. On the island, the silence is loud. The fog is thick. It mirrors her own mental state—clouded, cold, and unpredictable.
The house itself, inherited from the deceased Alice, is filled with "decrepit decor" and a "creepy attic." It’s practically a gothic novel set in the modern day. Kubica uses these elements to ramp up the dread until you’re jumping at every creak of the floorboards.
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Real-World Themes Hidden in the Fiction
Beyond the "whodunnit" aspect, the book touches on:
- The invisibility of rural healthcare: Sadie struggles with the lack of resources on the island.
- The cycle of trauma: How Imogen’s behavior is a direct result of the horror she witnessed with her mother.
- Gaslighting: The extreme psychological warfare Will wages on Sadie is a dark, exaggerated version of real-world domestic abuse.
How to Approach the Book Now
If you’re picking up The Other Mrs. for the first time, or maybe giving it a second look, don't just focus on the murder. Look at the language.
Kubica is a master of "sleight of hand." She tells you exactly what’s happening, but she phrases it in a way that makes you look in the opposite direction. It’s a masterclass in unreliable narration.
If you loved this one, you should definitely check out her other hits like Local Woman Missing or She's Not Sorry. She has this specific way of writing about suburban "perfection" that feels like it’s rotting from the inside out.
Actionable Insights for Thriller Fans
If you're looking to get the most out of your next psychological thriller read, or if you're trying to write one yourself, here's what you can learn from Kubica:
- Track the "Gaps": When a narrator says they "can't quite remember" or "lost track of time," don't ignore it. It’s almost always a structural clue, not just flavor text.
- Question the "Stable" Character: Often, the person acting as the "voice of reason" (like Will) is the one holding the match.
- Vary the POV: Using different ages or "voices" for the same character at different points in time is a high-risk, high-reward strategy for building mystery.
Check out the Author’s Note at the end of the book if you have a copy. Kubica explains a lot of her research into the setting and the mental health aspects, which gives a bit more context to the "why" behind the "what." Just don't expect to sleep easily after you finish that last chapter.
To truly appreciate the complexity of the plot, try re-reading the Camille chapters with the knowledge that she is Sadie's alter. You'll see the overlap in their lives and the subtle hints that they are physically in the same place at different times. Pay close attention to the interactions between Will and Camille—knowing now that he is intentionally triggering her shifts makes those scenes much more sinister. This perspective transforms the book from a standard mystery into a chilling study of psychological manipulation. Finally, compare the descriptions of the island from Sadie’s perspective versus Camille’s to see how the author uses tone to differentiate their internal worlds.