Cadence Sinclair Eastman
The narrator and protagonist of the novel, Cadence is the oldest of the Sinclair grandchildren. Cadence values her family and treasures the summers they spend together. She is in love with Gat, the nephew of her aunt Carrie's partner. After a traumatic brain injury that happens during summer fifteen on her grandfather's island, she appears to need more guidance and confidence-bolstering from her cousins who she feels are ignoring her, but she doesn't know why. As the novel goes on, it is revealed that Cadence is suffering from post-traumatic stress disorder, which prevents her from remembering exactly what happened. Cadence eventually pieces together her memory, recalling that she, Mirren, Johnny, and Gat (known to the family as the Liars) decided to burn down their grandfather's house on the island as a protest against the family's drunken fights over their inheritance. Drunk herself at the time, Cadence accidentally burns the main floor of the house while her fellow arsonists are still in the house. Cadence is the only Liar to survive.
Johnny Sinclair Dennis
Only a few weeks younger than Cadence, Johnny still assumes somewhat of a leadership role within the Liars, especially during Summer Seventeen when Cadence is finally allowed to return to Beechwood. He is particularly close to Mirren, and tends to assume responsibility for most of the Liars' exploits. Having been convinced by Gat and Cadence, Johnny takes part in the arson that leads to his death.
Gatwick Matthew Patil
Gat is Cadence's love interest. As Aunt Carrie's boyfriend's nephew, Gat has spent summers on Beechwood Island since childhood. Gat is of Indian descent; just as Granddad does not consider his uncle a suitable husband for Carrie because of his ethnicity, Gat is considered an unsuitable boyfriend to Cadence. Gat's frustration at Cadence's family's racism becomes a factor in his and Cadence's plan to burn down Clairmont.
Mirren Sinclair Sheffield
The youngest of the Liars, Mirren is Aunt Bess's oldest daughter, and third in the Sinclair grandchild pecking order. She is possibly the least disturbed about the fighting between the Sinclair sisters and was also the grandchild closest to their grandmother, Tipper. The post-death version of Mirren who interacts with Cadence during summer seventeen boasts of a boyfriend who doesn't exist. She also appears to be suffering from an illness that gets worse as the summer goes on.
Harris Sinclair (Granddad)
Harris is the head of the Sinclair family. Full of ideas about hard work and American traditions, he sets his children against each other and uses his wealth as a tool with which to control them. His manipulative behavior prompts the Liars to burn his house on the island. Following the loss of Clairmont, he rebuilds the house in a modern style and doesn't put any possessions in it. More subdued than he used to be, Harris treats Cadence with tenderness.
Tipper Sinclair
The Sinclair family matriarch, Tipper passes away just before summer fifteen. Although she is as concerned with propriety and appearances as her husband is, she does not have his Machiavellian personality and actually loves her children and grandchildren.
Penny Sinclair Eastman (Mummy)
Cadence's mother Penny is the middle Sinclair daughter. When her husband leaves her for another woman, Penny represses her emotions and immediately redecorates the house to erase her ex-husband's presence. Throughout the book, she advises Cadence to act normal and ignore the grief and dysfunction around her. When Penny's sister Bess tries to petition Harris to give Penny's larger house on the island to her, Penny pressures Cadence into advocating on her behalf. Following the tragedy of summer fifteen, Penny is gentle with her daughter, careful not to trigger her trauma by speaking of the fire.
Carrie Sinclair Dennis
The oldest of the Sinclair girls, Carrie is mother to Johnny and his younger brother Will. Out of fear she will be cut out of her racist father's will, she refuses to marry her long-time partner, Ed, though they continue to live together.
Bess Sinclair Sheffield
Bess is the youngest of the Sinclair girls and has four children, including Mirren, who is the youngest of the Liars. She is the one most concerned not to lose out in the inheritance race because of her position as the youngest daughter. Although Granddad tells Cadence she is a "grasping wench," he apparently promises to give Bess Penny's house, Windemere, because it has five bedrooms and Bess has more children.
Ed
Ed is Carrie's longtime partner and uncle to Gat. He accompanies her to Beechwood, but is often away for work. Harris does not approve of Ed and Carrie's relationship because Ed is Indian. Even though they have lived together for a decade, Carrie turns down Ed's wedding proposal out of fear her father will cut her out of the will. By the end of the book, Harris concedes that he doesn't like Ed, but Ed is staying with Carrie.
