The Lost Girls of Willowbrook (2022) by Ellen Marie Wiseman is a historical novel based loosely on events surrounding the discovery of abusive conditions in Willowbrook State School in the 1970s. The novel follows protagonist Sage Winters as she tries to discover what happened to her twin sister, Rosemary, after Rosemary goes missing from the institution’s grounds in December 1971.

The novel’s setting in a mental health facility and thriller genre places it in company with similar works, such as novels One Flew Over the Cuckoo’s Nest (1962) by Ken Kesey and Shutter Island (2003) by Dennis Lehane, as well as Susanna Kaysen’s 1993 memoir Girl, Interrupted. The novel’s focus on mental illness and institutional abuse evokes The Danger of Secrets, The Dual Nature of Imagination, and Deceptive Appearances.

Wiseman’s other historical fiction novels, including New York Times bestsellers The Life She Was Given (2017) and The Orphan Collector (2020), have received critical acclaim for Wiseman’s historical accuracy and compelling narrative.

This guide references the 2022 Kensington paperback edition of the novel.

Content Warning: The source material contains references to domestic violence, rape, sexual assault, institutional abuse, self-harm, suicide, and murder. The source material also uses outdated and offensive language to refer to people with developmental disabilities and people of color. The author notes the intentional use of this language to highlight the prejudices of the period.

Plot Summary

Sixteen-year-old Sage Winters discovers in late December of 1971 that her identical twin sister, Rosemary, did not die six years earlier. Instead, Sage’s mother and stepfather had Rosemary institutionalized in Willowbrook State School in Staten Island, New York. Disturbingly, Rosemary has recently gone missing from the school. Rosemary was a kind and dreamy girl who always saw the beauty around her. However, she also heard voices and had other symptoms of mental illness.

Sage decides to go to Willowbrook alone to try to find her sister. As she waits for the bus in the cold, she thinks of her mother’s death, her parents’ divorce, and the unsettling number of missing children in the area.

When Sage gets to Willowbrook, she is mistaken for Rosemary because of their identical appearance, Rosemary’s tendency to claim she is Sage, and because their mother never told the staff that Rosemary had a twin. Sage is taken into Willowbrook by force and sedated. None of the staff believe her when she tries to convince them of her true identity.

On her ward, Sage witnesses horrific living conditions and sexual and physical abuse of residents—what her sister has lived through for six years. Wayne Myers, one of the male attendants who oversees the dayroom where residents spend every day, is coarse and abusive to the women in his care. Norma and Tina, residents who were close to Rosemary, reveal that Rosemary was sexually involved, likely non-consensually, with Wayne. Eddie King, a janitor, is the only person who believes that Sage isn’t Rosemary. He offers to help her prove her identity and escape Willowbrook.

When camera crews unexpectedly come to Willowbrook to expose its terrible conditions and abuses, Eddie takes Sage into the tunnels below the school. There, they discover Rosemary’s dead body—posed, made up, and cut in disturbing ways. However, when Sage and Eddie tell Rosemary’s doctor, Dr. Baldwin, he refuses to believe them. Sage is placed in isolation as punishment for her escape attempt. Later, Baldwin tells her there was no body in the tunnels. After Sage tells authorities who called the camera crews, they reward her by taking her from isolation and placing her back on her ward. Eddie visits her late at night, confirming that Rosemary’s body has been removed from the tunnels, and telling her he hadn’t been able to contact any of her family or friends.

Police detectives arrive at Willowbrook following an anonymous tip about Rosemary’s body. They interview Sage and seem bothered by her rough treatment, but they allow her to be placed back on the ward. A short time later, Baldwin’s secretary Evie is found murdered in the woods on Willowbrook’s campus; her body looks like Rosemary’s body. The police again interview Sage, taking her to see the crime scene. While they investigate, they discover Rosemary’s body in a shallow grave. The police have also checked into Sage’s claims of not being Rosemary; after Rosemary is found, Sage is released.

At home, her stepfather is gone. After cleaning up and sleeping for a little while, Sage goes out to find food. Eddie appears, drives her to a diner, buys her breakfast, and they discuss Willowbrook. He drives her home and spends the night on the couch because she’s still afraid that Rosemary’s killer, who she believes is Wayne, may target her next. Eddie leaves early in the morning. Sage prepares to go stay with friends; in the process of packing, she discovers her stepfather’s mutilated body under his bed.

At the police station, Sage reports everything that’s happened between when she left Willowbrook and when she discovered Alan’s body. An officer interviews the diner waitress, and then the police take Sage back to Willowbrook: They have discovered Wayne’s body. Baldwin then reveals that Eddie is actually a Willowbrook resident, so he couldn’t have taken Sage to breakfast at her home. Baldwin convinces the police that Sage should be admitted to Willowbrook temporarily because she is having delusions. Sage is again sedated and taken to a locked room.

When she wakes, she bangs on the door, and Eddie unlocks it. He confesses that he has been killing Willowbrook residents as a mercy, and killing others he sees as threatening. He attacks Sage. She fights back, stabbing him with his own knife, and loses consciousness. She wakes in the Willowbrook hospital; when the police and a social worker discuss placing her in a group home, she tells them her father’s name. The next day, Sage’s father retrieves her from Willowbrook. Although Sage is traumatized and devastated by her sister’s death and Eddie’s attack, she heals with the help of her father and stepmother.

Sage dies of natural causes 73 years later. She has spent her life campaigning against Willowbrook and helping former residents find safe places to live.