Cadence explains that she comes from a family of “old-money Democrats.” Outwardly the Sinclairs are the picture of white, upper-class success, but privately some of them struggle with debt and addiction.
An unspecified accident has left Cadence weak, sickly-looking, and suffering from migraines. She dyes her blond hair black. At length, she relates the events leading up to the present point. When Cadence was fifteen, her father left her and her mother, Penny. Cadence was devastated, but Penny calmly packed the two of them off for their annual summer stay on the family’s private island, off the Massachusetts coast.
Years earlier, on their private island, Granddad and Granny Sinclair had built homes for themselves and each of their three daughters, Carrie, Bess, and Penny. Penny was younger than either of her sisters, but Cadence was older than any of her cousins—the children of her aunts.
Carrie had two boys, Johnny and Will. Bess had Mirren, Taft, and twins Liberty and Bonnie. The oldest children: Cadence, Johnny, and Mirren, are close. Since they were born within a few weeks of each other, the three named the summers after their age at the time. In “summer eight,” Gat arrived. His uncle, Ed, was Carrie’s boyfriend. Ed and Gat were of South Asian descent, which visibly bothered Granddad and Granny, but Gat and the three cousins soon became close friends. The rest of the family started calling the four of them “the Liars.” The reason is not given, but the cousins had not been “the Liars” before summer eight.
Gat was kind and funny, and by the end of summer fourteen, he and Cadence were in love.
Arriving on the island at the start of summer fifteen, after her parents’ breakup, Cadence walked in on Gat, unnoticed, as he was addressing a letter to another girl.
Cadence learned more about Gat's relationship with the other girl from her cousins but said nothing to Gat. She joined in games and campfire talk and listened as Gat criticized the Sinclair family's sheltered life.
Gat had been on a volunteer trip to India and had come back profoundly disturbed by the poverty there.
Cadence found herself still loving Gat but held back her feelings, until one day he declared his love for her while they were going through some old books in her attic.
As Cadence and Gat began to kiss, Granddad walked in, unannounced. He apologized for interrupting but told Gat he should watch himself. Cadence took the remark as a caution to Gat not to hit his head on the sloped ceiling, but Gat knew it was a warning to stay away from Cadence. Gat responded by going downstairs. Later, Cadence found him outside, upset, and kissed him again.
Granny had died the previous fall, and Granddad was in decline. The Sinclairs try to avoid talking about Granny after her death, but Gat wants to share fond memories.
Cadence’s accident came in July. She doesn’t remember much, but apparently she went swimming alone, hit her head on some rocks, and was found curled up on the beach, shivering. She was briefly hospitalized for hypothermia, pneumonia, and a possible head injury. Weeks later, she began having migraines. Testing produced a diagnosis of post-traumatic headache disorder, with warnings not to overuse her pain medication (later revealed to be Percocet). Throughout her ordeal, she heard nothing from the Liars. Gat’s silence was especially hurtful.
Arrangements on the island were disrupted as Granddad remodeled the house that he and Granny had lived in. Cadence’s emails to Johnny and Mirren during the Europe tour went unanswered.
For summer sixteen, Cadence’s father insisted on taking her on a grand tour of Europe. Her mother approved. The backstory narrative ends with Cadence’s return to Vermont. She attends school but admits that the other students are disturbed by her appearance and migraine episodes, and that she frequently visits the nurse’s office. At home, she discovers that Penny is keeping track of Cadence’s food intake.
Cadence tells the reader a tale of an aging king who tested his three daughters to see which one loved him best. The youngest daughter angered him with her response and is banished but eventually returns and wins back his affection. Realizing he is losing his mind, she pledges to stay and care for him—whether out of love or a desire to keep her inheritance, the daughter is not sure.
Cadence begins getting rid of personal possessions, including a copy of King Lear, which she read in school. She mails a couple of items to her cousins.
Cadence continues struggling to remember more of her accident. She used to ask her mother about it, but Penny would cry, telling Cadence that she had asked these questions many times. Cadence was always upset by the answers, Penny explained, but never remembered them. Finally, Cadence wrote the answers down. This is why she can now give at least some of the details.
Cadence’s father makes plans to take her to Europe again in summer seventeen, but she insists on returning to the island. The next day, a visibly failing Granddad comes to visit. Speaking with Cadence but failing to recognize her, he refers to her in the third person as the “future of the family.” Realizing his mistake, he pulls flowers from a nearby flowerbed in a gesture of apology.
Cadence tells the reader another story, of a king who stubbornly sent one daughter after another to plead with a dragon. The dragon simply ate all three. Cadence wonders whether the dragon or the father killed the girls. Penny and Cadence’s father quarrel but eventually agree that Cadence will spend the first month of summer seventeen on the island and the rest with him in Colorado.
Cadence gives away more possessions and plans to give Gat back a jacket she had borrowed.
Cadence learns from a phone conversation with Taft that Bonnie thinks Cadence is a drug addict. Taft is afraid the homes on the island are haunted.
Cadence arrives at the island. Granddad and Granny’s old Victorian house has been replaced by an unpleasant modern dwelling. A beloved tree swing is gone. Cadence is upset, but her mother orders her to pull herself together.
Bess hugs Cadence longer and harder than necessary. Bess’s family now lives at the new house. Granddad confuses Cadence with Mirren. Taft and the twins joke uneasily about Cadence’s vampire-like appearance.
The reunion with the Liars goes better, but Mirren intends to stay away from Granddad’s new house and “those people,” as do Johnny and Gat. Cadence is worried that the other Liars are moving on with life after the accident without her.
Cadence and Gat are finally alone together. She is still hurting from his silence during her recovery, but her old feelings for him return. Cadence reminds her mother that she got rid of all her father’s possessions when he left them.
Back in her old room on the island, Cadence starts picking out books to give away, despite her mother’s objections.
Cadence also resolves to fill in the gaps in what she knows about her accident.
That night, a sleepless Cadence encounters Carrie, out walking. Carrie mentions that Johnny is also sometimes up at night and that Will has nightmares.
The next day, Cadence learns from her Granddad that his two dogs recently died. He again confuses her with Mirren.
Cadence spends some time reconnecting with the other Liars. At least some of the items she sent never reached them. Mirren tells Cadence her aunts have been discussing the migraines she’s having, and Cadence asked Mirren not to feel sorry for her.
When Cadence finally confronts Gat over his silence while she was recuperating, he apologizes profusely.
Arriving at the new house for lunch, Cadence learns during a quick tour that Granddad’s old possessions are all gone. Carrie has no memory of talking with Cadence the night before.
When Cadence tries to get Taft to fill in some details about what happened two summers ago, he instead brings up the pills the twins found while poking around Cadence’s room.
Later, Mirren says that Bess feels slighted over the poor condition of Cuddledown, her house on the island where the Liars have been hanging out. When Johnny expresses surprise that Cadence is unaware of this situation, Mirren chides him for forgetting that Cadence doesn’t remember much of summer fifteen.
Cadence tells the Liars how sick she felt while in Europe.
Later, Cadence recalls a family conversation, just before her accident, that turned unpleasant when Granddad talked of selling the big house back in Boston. Cadence wonders why her mother and aunts are kinder to each other now.
The Liars talk about personal mottos. Mirren emphasizes kindness, while Gat emphasizes the need to fight evil. Cadence writes her motto on the back of her hands: “Always do what you are afraid to do.”
When Gat and Cadence are alone and begin to kiss, he pulls back, saying there’s much about him she doesn’t understand, including his experience as a person of South Asian descent, living among white people.
Cadence narrates yet another story of a king with three daughters. The youngest gave birth to a little girl of her own, tiny enough to fall in love with a handsome, clever mouse. When their love scandalized the kingdom, the tiny girl and the mouse escaped together to a foreign land.
Granddad takes Cadence on a day trip to a nearby town, where they run into his estate lawyer. Granddad proudly introduces Cadence as the first grandchild.
Cadence later recalls a conversation between her and Granddad over some statues, including statues made of ivory, that he had bought for Granny. Granddad had become irritated when Cadence remarked that ivory was illegal. She should not tell him what to do with his money, he had said.
Cadence worries that the other Liars aren’t being careful enough to avoid sunburn. She continues trying to fill the gaps in her memory.
Cadence and Mirren sneak away on a boat outing. Mirren claims not to know why Gat was out of touch for so long, and the conversation ends when Mirren begins to feel sick.
The Liars discover that one can picnic on Cuddledown’s roof.
As the days pass, the atmosphere at Cuddledown grows less enjoyable. Mirren constantly feels unwell, and Johnny wastes time with silly games. Gat spends all his time reading and has withdrawn from Cadence. Dirty dishes and even broken bottles begin to pile up.
Cadence finds Johnny playing with Legos. She presses him about why he didn’t respond to her emails after the accident. He blames it on his being a jerk but won’t answer her questions about Gat, beyond saying that Gat treated the other girlfriend badly and was angry with himself over many things.
Cadence leaves one of her giveaway books in Gat’s room in Cuddledown. The room, formerly Taft’s, is a filthy mess.
Cadence and Gat finally have an open conversation. Gat is annoyed with Cadence over her complaining and sympathy-seeking. She leads a privileged life, he says, that includes things like a trip to Europe paid for by her Granddad (not her father). Cadence accepts what Gat says, but she pleads that the pain of the migraines sometimes just makes her want to die.
Mirren continues to feel sick. She counsels Cadence not to keep trying to resume her relationship with Gat, because it will end in hurt for both of them. Mirren confesses to having made up stories about having a boyfriend of her own.
When Cadence rejoins the Liars after a two-day migraine, they talk about a beloved donut shop. Oddly, the others say things Cadence knows to be false.
Gat comes into Cadence’s room and sees the wall on which she has been posting clues about her accident. He comes clean about his other relationship. That night, Cadence again sees Carrie sleepwalking, and she hears Will cry out during a nightmare.
Cadence wants to give Johnny a box of Legos, but he has lost interest. At his suggestion, she gives them to the younger cousins.
The Liars go kayaking, even though Mirren is ill, and Cadence is supposed to be careful due to her head injury. Ignoring the others’ warnings, Cadence follows Johnny and Gat in a dangerous jump from rocks into the water. She resurfaces safely but wonders about alternate realities where she was killed or something else turned out differently.
That night, Cadence wakes from sleep with a memory of Carrie running and crying hysterically. Finding Mirren on the front porch, Cadence insists on knowing what occurred before her accident. Mirren won’t say much but doesn’t challenge Cadence’s speculation about being the victim of some sort of attack or tragedy.
In the morning, Cadence finds a new tire swing in front of her house, to replace the one gone from Granddad’s lawn. Inside is a gift of dried roses from Gat.
Cadence tells another story about a king with three daughters. The younger two gave birth to girls. The oldest gave birth to twin boys, one of which was a mouse. He was tidy and clever, but everyone was disgusted with him, so he left to see the world. Someday, he thought, maybe he would come back and burn the palace to the ground.
Cadence wakes early on the first day of her last week on the island. She now remembers that the four Liars deliberately set fire to Granddad’s old house, while the adults and younger cousins were on an outing off of the island. The fire consumed the house and everything in it.
Confronting Johnny, she learns that in summer fifteen, the aunts had begun quarreling openly over their shares of Granddad’s estate, including his island house and its contents.
Granddad had egged the aunts on by talking half-seriously of leaving a large share of the estate to Harvard University.
At Penny’s insistence, Cadence had lobbied Granddad to let Penny keep the house she and Cadence were living in. Granddad had responded by promising the house to Cadence, but she had then learned from Mirren that Granddad had also promised the house to her and Bess.
During a nighttime walk a couple of days later, Gat had explained to Cadence the meaning of Granddad’s warning to Gat during the attic visit. Granddad was a racist, Gat had said. Carrie had refused a marriage proposal from Ed because she knew Granddad would disinherit her if she accepted.
Cadence recounts a story of a merchant with three daughters. He steals a rose from a garden, as a gift for his eldest, but when the garden’s owner catches him, the merchant is forced to give up his eldest daughter as punishment. The owner looks like a beast but is in reality a cultured and sensitive man. The merchant never sees past the fearsome appearance.
Cadence recalls that during a nighttime pantry raid at the old house, she and Gat overheard the three aunts quarreling bitterly. The conversation was mostly about their inheritance, and it makes Cadence realize how much the aunts depend on Granddad’s money. Carrie slapped Bess over a taunting comment about Ed and Gat being outsiders.
Open conflict over Gat’s place in the family followed. When Carrie asked Gat to stay away from family meals for a while, the Liars all stopped coming. Cadence refused to break up with Gat as Penny demanded. The Liars took their revenge on the adults by secretly destroying Granddad’s statue collection.
The Liars began thinking: what if God struck Granddad’s house and it went up in flames? Maybe the adults would repent and learn to love one another again.
At a lunchtime confrontation, Penny threatened to leave with Cadence and never come back. Granddad responded by denouncing all three daughters for failing to uphold the family’s values and yet expecting him to support them financially.
As Cadence shares these fresh memories with the other Liars, more of what happened comes out. After the showdown with Granddad, all the adults angrily left the island, taking the younger cousins with them.
The Liars stayed on the island. Cadence remembers that after getting drunk, they burned Granddad’s house to the ground. She and Gat formed the plan and persuaded Johnny and Mirren to join in.
The Liars used gasoline from the boat shed to set fires in all four levels of Grandad’s house, with Cadence handling the ground floor. Cadence is pleased to learn that their plan apparently worked since the adults get along better now. Mirren observes that the aunts are miserable and drink heavily. Gat ventures that Granddad built the unpleasant new house as self-punishment. When Cadence questions this theory, Gat asks why she gave away all her belongings. He, Johnny and Mirren drift off to sleep soon after.
Cadence returns home and demands to know from Penny why the rest of the family hasn’t spoken in front of her about the fire. Penny responds that in the past, Cadence was upset by what Penny said about the fire.
Going up to her room, Cadence finds Mirren waiting. Mirren admits, apologetically, that she never read Cadence’s many emails. They read the emails together on Cadence’s laptop.
When Mirren leaves, Cadence suddenly thinks of Granddad’s two dogs. He had a habit of locking them in an upstairs bedroom, and she realizes they were trapped there as the house burned. She is responsible for their deaths.
When Mirren leaves, Cadence starts typing everything she remembers. This leads her to remembering what happened to Granddad’s two dogs. Sobbing as she runs across the island, she encounters Gat.
Cadence and Gat embrace. When Cadence explains that she’s crying because she killed the dogs, Gat asks if that’s everything. Cadence asks what more there might be, but Gat sorrowfully refuses to elaborate. He leaves to go back to Cuddledown.
Cadence remembers her hospitalization. Penny and Granddad were at her bedside. Her burned hands and feet were heavily bandaged.
Cadence struggles to relate another story, which eventually comes out as a tale about two boys and a girl whose lives were ruined when a witch, in the form of another girl, persuaded them to burn down their parents’ castle.
Cadence finally understands: Gat, Mirren, and Johnny all died in the fire. As far as the surviving family knows, the fire was an accident started by a jug of overturned motorboat fuel. The Liars and the dogs were trapped in the house, and Cadence was burned trying to save them. Her migraines and amnesia are symptoms of suppressed grief and guilt. The doctors treating Cadence suggest that she not be continually reminded of the tragedy, and that she should be allowed to remember what happened in her own way. She should also not return to the island until she has time to heal.
The truth, Cadence now remembers, is that she and the others, drunk, were careless in how they set the fire. The ground floor was fully aflame before the others could make their way out of the basement and upper floors. Cadence barely got out herself. When she realized the others were still in the house and tried to go back to save them, it was too late.
Cadence is filled with guilt over what she did, and with grief on behalf of Granddad, the three aunts, and the surviving younger cousins. She thinks about all the good qualities Johnny, Mirren and Gat each possessed, their dreams and ambitions, and their futures, which death has robbed from them. She realizes that they have remained on the island as ghosts only because she still needed them.
Cadence realizes that Penny suspects the truth of how the fire started and loves Cadence all the same.
At Cuddledown, Cadence has one last reunion with the Liars. They (especially Mirren) have been finding it harder and harder to stay on the island. The goodbyes at the beach are a mix of regret and tenderness. After a last hug from Gat, Cadence watches the Liars swim out to sea.
Cadence joins the family for lunch and begins to settle back into the rhythms of family life. She accepts an invitation from the twins to go boating the next day.
Granddad admits, during another town trip, that he doesn’t like Ed, but he acknowledges that Ed has stuck by Carrie. Cadence goes to Cuddledown and begins cleaning up the mess that built up as she spent time with the Liars.
Cadence tells one last tale, of a king and his three daughters, and the daughters’ children. The fiery deaths of some of the children drove the daughters to despair and the king to madness, but in the end the family survived. For outsiders, the tragedy is a source of glamour and mystery. For the surviving children, it is an ugly, confusing tangle of secrets.