Meet Grace. She's a successful marriage counselor in NYC who's being interviewed by Vogue about her new book. It's a hot take on relationships called "You Should Have Known" (Where have we heard that before?). Her bombshell thesis is that every relationship comes with warning signs, so if your relationship goes south, it's on you…because, well, you should have known.
As you can probably tell, Grace is pretty judgmental when we first meet her. She prides herself on her comfortable Upper East Side life, her brilliant pediatric oncologist husband, and her musically gifted son who attends her hoity-toity private school alma mater.
Speaking of which, Grace and some of her wealthy acquaintances are on the school's fundraising committee. Their planning meeting is interrupted by a new member: Malaga Alves, a quiet, beautiful Colombian woman who doesn't speak fluent English. To the horror of the Ladies Who Lunch, Malaga has the audacity to breastfeed her hungry baby girl during the meeting. Everyone's awkwardly trying not to look while sending silent OMG eyes around the room.
Flash forward, and it's the evening of the aforementioned glitzy-ritzy fundraiser. Grace is manning the check-in table and noting people who aren't there—including her own husband, Jonathan, who told her he was sitting shiva with a patient's family and would be there ASAP.
Grace joins the party and takes in the glamorous surroundings. All the women are gussied up with designer gowns, perfect nails, and styled hair—that is, all except Malaga Alves. She's wearing a simple rose dress and a gold cross necklace, and naturally she's the one who's surrounded by men. Iiiinteresting.
The fundraising auction begins and honestly, the party's attendees are so obnoxiously wealthy that we'll just say the bidding reaches $11,000 for a literal glass of "New York City tap water." That pretty much sums it up. The auction ends, everyone congratulates each other on being so rich (not really…but kind of), and Grace heads home to support Jonathan after such a tough day.
A few days later, Grace's phone is blowing up with texts and emails like she just got nominated for a Grammy. She's so busy trying to juggle publicity interviews for her new book, her clients' therapy appointments, and typical parent stuff that she doesn't check them for a while. When she finally does, she learns there's big news in her social circle: Malaga Alves has been murdered.
The murder sets off a frenzy of unwanted attention. Reporters stake out the private school. Detectives confront Grace outside her apartment. Grace thinks it's all a little much and doesn't understand why people assume she knows anything. She tries to call Jonathan at his pediatric conference to vent about the chaos, but she finds his cell phone hidden on the nightstand. Uh-oh.
Grace's mind is reeling with possibilities, but she's trying not to freak out. This goal proves to be more difficult than expected as she gets hit with one world-shattering revelation after another over the next few chapters:
Jonathan's not at a pediatric conference.
He doesn't even work at the hospital any more.
He was fired nine months ago after multiple warnings.
He was having an affair with a patient's mother: Malaga Alves.
He paid for Miguel's tuition under the guise of helping his former patient.
He's the father of the baby girl Malaga was feeding at the committee meeting.
Malaga was pregnant when she died, and Jonathan is (of course) that baby's father as well.
Therefore, he's the prime suspect in her murder—and the police have no idea where he is now.
Naturally, the next logical step when someone realizes her husband is a pathological liar is to tell the story of her great-grandparents. Um, what? When we flash back to reality, it turns out this random break in the story actually is somewhat relevant: Grace and her son Henry are headed for her family's lake house in an effort to get the heck out of "Dodge the Media" NYC.
Despite the house's lack of winterization and Wi-Fi, Grace and Henry try to make the best of their new circumstances. Using the public library's computers in allotted increments, Grace shuts down her therapy practice and cancels Henry's violin lessons. She also runs into their closest neighbor, Leo, who invites her and Henry over for dinner after New Year's.
Grace's dad, Frederich Reinhart, surprises her by showing up for Christmas. In a classic dad move, he brings a feast of Grace's favorite comfort foods from the Jewish deli, plus gifts for Henry. He launches into a fatherly pep talk, but it soon turns depressing when he reveals that Jonathan asked him for $100,000 to pay private school tuition. As Grace now knows, that money wasn't for Henry but for Miguel Alves. Papa Reinhart also reveals that he and Grace's mother weren't happily married despite putting up a good front—which is fitting, since Grace always considered her parents the barometer for a happy couple.
After the holidays, Grace is forced to enroll Henry in (gasp!) public school, but he makes friends quickly and plans to try out for the baseball team. Meanwhile, Grace continues to learn new things about her husband:
In the face of all these revelations, Grace decides to get a dog—they always refrained from doing so because Jonathan was allergic. Henry names the dog Sherlock, and then he finally works up the courage to ask his mom if they're ever going to talk about what happened. They have a heart-to-heart about it, and Grace realizes Henry has grown so much in the past few months. Learning your dad's a murderous cheater and an international fugitive probably shatters whatever childhood innocence one may possess.
Grace and Henry finally take Leo up on his dinner invitation and meet all of his bandmates. While Leo's friends are teaching uptight violinist Henry to play the fiddle, Grace and Leo kiss, and then Grace heads home to check on their dog. Perfect timing: She has a letter from Jonathan, giving her instructions on how to join him in Canada.
For a moment, Grace considers what this would even look like...and then she calls the cops.
The book ends with Grace packing up her apartment in NYC. One of the detectives arrives to tell her they've found Jonathan, not in Canada, but in Brazil—one final act of deception. Grace barely cares enough to be shocked. She realizes that, like Henry, she too has become a different person than she was at the beginning of the book.
As a pensive-but-hopeful cover of Fleetwood Mac's “Landslide” begins to play, we fade to black on Grace listening to the sounds of the elevator descending, carrying the detective back to the lobby "and the street where she used to live" (24.438). We may have taken some artistic license with that, but you get the idea.