Blood in the Water

The novel opens with an unnamed narrator plunging into a dark, ice-cold ocean at night, struggling toward rocks beneath a bridge and wondering if a murderer is watching.

The story jumps back to the beginning of summer. Twelve-year-old Kaylani McKinnon, a Black girl from Brooklyn, takes a phone call from her father through the prison Inmate Calling Service. He is serving a minimum of seven to ten years for embezzlement, a charge Kaylani firmly believes is false. A robotic voice announces their remaining time. Her father encourages her to embrace a summer trip to Martha's Vineyard, where she will stay with the Watsons, an elderly Black couple close to her grandmother's family for decades. The Watsons funded her father's private school education and helped him get his job. Her father reminds her to be herself and stay honest. Kaylani has secretly attended a mock trial workshop and plans to study for a pre-law camp entrance exam as part of a mission she calls #operationFREEDAD. She agrees to the trip but vows to spend the time studying rather than vacationing.

Mr. Watson drives Kaylani to the ferry, where she meets his granddaughters: twelve-year-old London Watson and sixteen-year-old Cassie. London mocks Kaylani's seasickness, her iPod, her lack of a cell phone, and her love of the rapper J-Roc. The group arrives in Oak Bluffs and drives to the Watsons' large gray mansion near the East Chop Lighthouse. Chadwick Cooper, a charming teenage family acquaintance about Cassie's age who has stopped by to drop off his mother's fundraiser tickets, gives Kaylani a tour and challenges her to discover who owned the house before the Watsons, calling it a mystery. Mrs. Watson shows Kaylani old photos, including one with the Obamas. Kaylani fantasizes about meeting the former president, hoping a connection might help free her father.

London treats Kaylani as a charity case, a suspicion confirmed when Kaylani overhears Mrs. Watson telling London to help "the less fortunate." London bikes Kaylani through town, showing her the gingerbread cottages, the Inkwell (a historically significant beach for Black visitors), and the Jaws bridge, where locals jump into the water in a tradition named after the movie Jaws, which was filmed nearby. That evening at the Circuit Avenue arcade, Kaylani meets Miles Cooper, Chadwick's younger brother. London strikes a deal: If Kaylani quietly accompanies her to spy on Cassie at a beach bonfire, London will let Kaylani use her phone, giving her father a way to reach her.

At the bonfire, Chadwick bonds with Kaylani over J-Roc. When Kaylani mentions her father handled accounting work for the Watsons, including deeds, Chadwick's demeanor shifts abruptly. He walks to the shoreline, staring at his phone with a troubled expression. Jaden Gibbons, a local boy who does groundskeeping for the Watsons, arrives and approaches Cassie. Chadwick confronts Jaden, and a fight breaks out, ending with Jaden bloodying Chadwick's nose. The party scatters when police lights appear. Cassie stays behind with Chadwick, and Kaylani sees her climb into his truck.

The next morning, Mrs. Watson announces Chadwick is missing. London lies about the previous night and threatens to revoke Kaylani's phone access if she tells the truth. Later, Chadwick's body is found at the Jaws bridge. Rumors blame a shark attack, but Kaylani notices fresh tire tracks near the railing that police overlook. Miles insists something does not add up: Chadwick was an excellent swimmer who had jumped off the bridge many times, and his car was not at the scene, meaning someone else was with him.

Detectives visit the Watson home and reveal Chadwick's death is a homicide: He suffered blunt force trauma to the back of the head and had no water in his lungs, meaning he was dead before entering the water. The wound was made to resemble a shark bite using a sharp tool. Cassie's fingerprints were found in his truck, and she was the last known person to see him alive. London insists Cassie is innocent and begs Kaylani to help. Kaylani investigates: She finds stained sandals and car keys in Cassie's room, locates surveillance footage showing Cassie leaving the truck and a second car arriving shortly after, and attends a presentation by a shark biologist confirming the bite was faked. Miles joins Kaylani and London in their search for the killer.

Cassie retaliates by buying Kaylani expensive clothes, then pressuring her to jump off the bridge despite knowing Kaylani cannot swim well. Miles intervenes. The Watsons then accuse Kaylani of stealing charity money, citing the new clothes. London turns on Kaylani, calling her father a "jailbird" and revealing she gave Kaylani a fake phone number, meaning her father's calls have gone to a stranger for weeks. Kaylani keeps her composure, pointing to security cameras that would reveal the real thief. She storms out. Miles gives her his real number, and through his phone, Kaylani finally speaks with her father again.

Kaylani deepens her research into Alice McBride, the house's original owner. On a heritage trail tour, a guide explains that McBride raised money for civil rights causes, died in a drowning accident, and left the house to the Watsons in her will. Yet all traces of McBride have been erased from public records. In Chadwick's bedroom, Kaylani and Miles discover his research: photographs of Alice standing in front of the Watson house. Ms. Marguerite, the Watsons' longtime housekeeper, becomes shaken when asked about Alice, admitting Alice gave her a home and a job before cutting herself off. Police recover Chadwick's phone from the arcade; his last search was about Kaylani's father's fraud trial. The three young investigators realize the killer held the phone and turned it in as a warning.

Kaylani visits Jaden, who reveals Mrs. Watson promised to help him win Cassie's affections in exchange for unspecified favors. Police arrest Jaden for Chadwick's murder before he can elaborate. At the Watson house, Cassie reveals that Chadwick told her the Watsons stole the house from its rightful owner and had proof. Mrs. Watson announces she is driving Kaylani off the island. While loading the car, Kaylani discovers Chadwick's wallet containing his J-Roc concert tickets and a bag of sharp gardening tools in the trunk. She realizes Mrs. Watson is the killer. To warn London, she says something deliberately out of character: that J-Roc is not the best rapper. London recognizes the impossible concession as a signal.

Mrs. Watson drives not toward the ferry but toward the Jaws bridge. She confesses to framing Kaylani's father because his accounting work was leading him to uncover the truth about the house. She killed Chadwick because his research into Alice McBride threatened to expose her. She also implies she killed Alice years ago to take the house, forging a will. At the bridge, she forces Kaylani onto the railing and shoves her off. Kaylani remembers the boy she watched jump on her first day, holds her nose, falls straight, and survives the impact. Police arrive and rescue her. London had called them after noticing Mrs. Watson drove the wrong direction, checking ferry schedules and finding none running, and recognizing Kaylani's J-Roc remark as a distress signal. Jaden, already in custody, had been confessing his role in disposing of the body, corroborating London's alarm.

Mrs. Watson is arrested. Ms. Marguerite confirms the will was forged in Mrs. Watson's handwriting, and police charge Mrs. Watson with both Chadwick's and Alice McBride's murders. Her scheme to frame Kaylani's father is exposed, and Kaylani's mother begins working with lawyers to clear his name. On the ferry home, London apologizes for her cruelty and admits she was lonely. Miles gives Kaylani a seasickness band, and they exchange numbers. Kaylani looks out at the water: not a shark in sight.