Riley Sager’s 2019 New York Times Best Seller Lock Every Door is a psychological thriller set in New York City. When Jules Larsen, the protagonist and first-person narrator, gets an opportunity to apartment-sit at the Bartholomew, an illustrious Manhattan apartment building, she sees potential financial security and a foray into a new social strata. However, when another apartment sitter named Ingrid Gallagher disappears shortly after Jules’s arrival, Jules starts probing into the Bartholomew’s shrouded history and its secretive residents’ pastimes. The more she finds out, the less safe she feels. The novel explores the themes of Psychological Effects of Isolation and Loneliness, the Pursuit of Truth in a World of Deception, and Wealthy–Vulnerable Power Dynamics.

Sager is the author of eight novels, including the bestsellers Survive the Night and Home Before Dark. His work has been published in over 30 countries worldwide. He has been widely reviewed, and his work has been praised by writers such as Stephen King and Ruth Ware.

This guide refers to the 2020 Penguin Random House paperback edition of the novel.

Content Warning: The source text references multiple deaths by suicide and deals with the psychological effects of trauma, loss, and grief. It also uses stigmatizing and potentially offensive language to refer to people experiencing mental illness.

Plot Summary

After losing her job and breaking up with her boyfriend, 25-year-old Jules Larsen responds to an apartment-sitting ad. She’s shocked to learn that the job site is the celebrated Bartholomew apartment building on Manhattan’s Upper West Side. Jules feels that she doesn’t belong in this setting, but she’s had an attachment to the building since reading Greta Manville’s novel Heart of a Dreamer as a child.

Jules accepts the temporary tenant position in the Bartholomew’s 12A unit. She moves out of her best friend Chloe’s apartment, dismissing Chloe’s concerns about the job. The Bartholomew’s manager, Leslie Evelyn, gives Jules the apartment sitters’ code of conduct. The rules are rigid, but Jules needs the money.

Jules befriends the apartment sitter who lives below her, Ingrid Gallagher. They have lunch in the park and discuss their similarities. Later that night, Jules thinks she hears her screaming and knocks on Ingrid’s door. Ingrid assures Jules that she is fine, but the next morning, she is gone. Jules tries to find Ingrid, asking the tenants about their relationships with her and searching local hospitals and shelters, but all her efforts fail.

One day, Jules’s neighbor Dr. Nick and another resident, Greta Manville, Jules’s childhood favorite author, offer to help her find Ingrid. They give her suggestions and encourage her search. Jules discusses Ingrid with another apartment sitter, Dylan, who reveals his suspicions about the Bartholomew. He tells Jules that other apartment sitters have gone missing in the past, including the young woman who once occupied 12A. Unsettled, Jules redoubles her investigative efforts, delving into the Bartholomew’s shrouded history. Her findings convince her that the Bartholomew’s residents, including Nick and Greta, are members of a Satanist cult. Convinced that they plan to kill her and sacrifice her organs to the devil, Jules tries to flee. However, Nick apprehends her before she can escape.

Nick reveals that his great-grandfather, Dr. Thomas Bartholomew, established the Bartholomew as a protective realm for the wealthy, elite classes. He devoted himself to ensnaring vulnerable individuals and harvesting their organs for ailing, prominent members of society. After Thomas’s death by suicide, Nick adopted his philosophies and renewed his work at the Bartholomew. Over the years, he captured and killed numerous other apartment sitters, stole their organs, and conducted illegal transplants. Nick takes one of Jules’s kidneys for Greta and plans to take her liver and heart next. Later, with her attendant distracted, Jules procures a lighter and sets her room on fire. While Nick and his team investigate the issue, she escapes the Bartholomew. Once she makes it into the street, she watches Nick throw himself off the top of the apartment building.

Over the next six months, Jules reestablishes her life. She returns to the Upper West Side for the Bartholomew’s demolition and cries while watching. She recalls that, after the fire, the police thoroughly investigated the Bartholomew and shut down its illicit operations. Everyone involved is under prosecution except Greta, who is in hiding. Jules wishes Greta would answer for her crimes, but she’s glad that her own work helped give the missing apartment sitters’ families closure.