Joel visits Bookland and buys a copy of Wuthering Heights, then asks Cassie out on a date.

Joel's friend Rob mistakes Cassie for Francesca on their first date, describing Francesca as brilliant and beautiful.

Cassie arrives at Bookland to find the facade covered in red paint that looks like blood.

Cassie meets Joel's couple friends at the Central Park Zoo and learns she looks exactly like Francesca.

Cassie sleeps with Joel to test her feelings; the next morning she finds 'SLUT' painted on her door.

Lydia invites Cassie to her Halloween party and specifically suggests that she dress as Cleopatra.

Cassie finds a party photo showing Francesca in the identical Cleopatra costume and realizes Lydia deliberately set her up.

Joel tells Cassie he loves her and gives her a key to his apartment.

At an awkward dinner, Lydia reveals that Francesca is the godmother of her daughter Violet.

Joel saves Cassie's life with an Epi-pen after she suffers a severe allergic reaction to peanuts.

Joel reveals to Cassie that Francesca died by suicide shortly after he broke up with her.

Cassie finds 'slut' written inside her closet and realizes the person harassing her has a key to her home.

Cassie calls Anna for help after discovering that someone with a key has been inside her apartment.

Lydia arrives at Cassie's apartment with poisoned wine, confesses her resentment over Francesca's death, and Cassie passes out.

Cassie wakes in the hospital, learns that Anna and Joel once dated for ten years, and reaffirms her love with Joel.

Cassie Donovan, owner of a struggling Manhattan bookstore, meets and falls for Joel Broden, a handsome doctor, but their relationship is haunted from the start by the mysterious presence of Joel's ex-girlfriend Francesca. Cassie begins experiencing targeted harassment at her home and business, and Joel's friends — especially Lydia — are openly hostile, making her feel unworthy of Joel's world. Key moments such as Lydia's deliberate Halloween costume trick and the revelation that Francesca is Violet's godmother deepen Cassie's insecurities and sharpen her suspicion that someone is out to destroy her relationship. When Joel finally reveals that Francesca died by suicide after their breakup, Cassie realizes the harassment must be coming from someone else entirely. The terrifying truth arrives when Lydia appears at Cassie's apartment with poisoned wine and confesses her resentment over Francesca's death, leaving Cassie unconscious and fighting for her life. Cassie is rescued, wakes in the hospital, reaffirms her love with Joel, and eventually accepts his marriage proposal.

The main plot of Cassie and Joel's relationship.

Joel tells the Ex he will no longer pay rent on their shared apartment, forcing her to find new housing.

After rejecting a tiny micro-apartment, the Ex accepts her grandmother's offer to move in together in Brooklyn.

After their first kiss, Cassie senses someone following her on her walk home from the train station.

The Ex briefly deletes the WhereAmI app after being embarrassed by Lydia but quickly re-downloads it and continues stalking Joel.

Cassie decides not to report the 'SLUT' vandalism to police, fearing they will find her grandfather's forged books.

The Ex steals Olive's keys from her purse at a Starbucks and has copies made at a nearby hardware store.

Anna follows Cassie out of Lydia's Halloween party, comforts her, and promises to visit Bookland.

Cassie arrives at Bookland the morning after the Halloween party to find the store broken into and trashed.

The Ex calls Dean to examine her grandmother's heart pain; her grandmother agrees only if the Ex will date Dean.

Cassie and Joel visit Anna and Con's newborn baby; Cassie worries that Joel wants children sooner than she does.

The Ex's private detective cousin reports that Olive's business is failing and she is in debt to dangerous sources.

Pete gets drunk at dinner with Cassie and Joel and implies to Cassie that he wants to divorce Lydia.

An old woman brings a collection of expensive first editions to Bookland, prompting Cassie to consider more drastic financial measures.

Anna finds Joel drinking alone at Francesca's restaurant and tells him she believes Lydia is stalking Cassie.

Cassie finds Francesca's gold rose necklace in Anna's drawer and realizes Anna killed Francesca but decides to keep the secret.

In the aftermath of her breakup with Joel, the Ex loses her financial support when Joel ends their shared lease, forcing her through a humiliating housing search before she moves into her grandmother's Brooklyn apartment. Meanwhile, Cassie is quietly terrorized by anonymous vandalism at her bookstore and home, all while concealing her grandfather's illegal book forgeries from the police. The two storylines are shaped by the same tight-knit social circle: Pete and Lydia, whose marriage is quietly unraveling, and Anna and Con, whose new baby draws Cassie and Joel closer together. Key discoveries accumulate on both sides — the Ex's cousin uncovers Francesca's dangerous debts, Pete confides his desire for divorce, and an old woman's rare books force Cassie to confront the bookstore's dire finances. In the final act, Anna tracks Joel to Francesca's restaurant and identifies Lydia as Cassie's stalker before it is too late. The epilogue delivers the last and darkest revelation: Cassie quietly discovers that Anna is responsible for Francesca's death but chooses to say nothing.

The secondary events and subplots shaping both storylines.

Joel breaks up with the Ex at dinner, claiming he needs to make serious life changes after losing a patient.

The Ex follows Joel's new girlfriend home from their date, energized when she senses the woman is frightened.

While stalking Joel in Central Park, the Ex meets his friend Dean at a hot dog stand and declines his invitation.

Cassie visits Francesca's restaurant and unexpectedly runs into Joel on the same block, suspecting he is still in love with Francesca.

Joel meets the Ex at a bar and firmly demands she move on; she flees without responding.

Anna visits Bookland and reveals she never liked Francesca, calling her 'sort of nuts,' before being interrupted by a customer.

The Ex visits Dean's medical practice and later shares a magical first kiss with him after a dinner date.

The Ex uses WhereAmI to track Joel, warns him about Olive's dangerous debts, but Joel deletes the app and calls her crazy.

Dean confronts the Ex outside her workplace about her silence, tells her he feels a genuine connection, and walks away.

It is revealed that 'the Ex' is Anna, and the new girlfriend she has been stalking is Francesca, not Cassie.

Anna confronts Francesca at her apartment; Francesca admits Joel broke up with her over debt but reveals she has another secret.

It is revealed that Dean's real name is Constantine, making him the same person as Con from the other chapters.

Lydia tells Anna and Dean that she blames Joel for Francesca's death and resents Cassie for replacing Francesca.

Anna and Joel arrive at Cassie's apartment to find Lydia standing over an unconscious Cassie and call an ambulance.

Joel proposes to Cassie; Anna's perspective reveals she killed Francesca and had intended for Joel to be arrested for the murder.

The novel's most pivotal moments begin in the prologue, when Joel's breakup with the Ex sets her obsessive behavior in motion and foreshadows a murder. As the Ex stalks Joel's new girlfriend, she unexpectedly meets and develops genuine feelings for Joel's friend Dean — a relationship that gains new significance when it is later revealed that Dean and Con are the same person, Constantine, meaning the Ex married into Joel's own social circle. The novel's central twist arrives when it is revealed that the Ex is actually Anna, and the woman she has been stalking is Francesca — not Cassie — completely reframing the narrative's timeline and Anna's role in it. Anna's confrontation with Francesca, Lydia's confession of blame and resentment, and the dramatic rescue at Cassie's apartment all cascade toward the epilogue's darkest revelation: Anna killed Francesca, staged it as a suicide, and had intended for Joel to be arrested for the crime. These turning points transform what appears to be a story about jealousy and heartbreak into a layered thriller about obsession and premeditated murder.