The Unknown: A Novel

In 1926, five women disappeared from a remote island in Vermont. Now, one hundred years later, it’s happening again.

Struggling actress Marin Keane is shocked when she lands a role in a major motion picture about the unsolved mystery of New Avalon, an island on sprawling Lake Faraday in Vermont. She’s even more surprised when she learns that the role requires a weeklong research trip to that very spot.

Because New Avalon isn’t your ordinary island. A century ago, it was a commune for spiritual mediums—until they all vanished in 1926. The only trace of them was five dresses hanging from the branches of an old oak tree in the middle of the island, one for each missing woman. Some locals say they simply left. Others think they were murdered. But the prevailing opinion, thanks to a diary left behind by one of the vanished, a young woman named Daisy Rue, is that a séance gone wrong conjured something supernatural that took them all one by one.

Not long after arriving, Marin and her castmates, including legendary actress Violet Wright and white-hot director Ronan Peters, begin to realize all is not right with New Avalon. They hear strange noises in the night and notice mysterious symbols left behind by the island's previous occupants. And after a sudden health emergency leaves Marin, Ronan, and the other actors stranded on the island, the disappearances begin again.

Is it the work of someone trying to derail the movie? Or is the island’s alleged supernatural past catching up with the present? As fear and suspicion mount, Marin turns to Daisy’s diary, hoping it holds the key to figuring out what really happened to the women of New Avalon—and how to keep the island’s terrible history from repeating itself.

Riley Sager is the New York Times bestselling author of nine novels, most recently Middle of the Night and The Only One Left. His books have been published in over 35 countries, with more than 3 million copies sold worldwide. His latest book, With a Vengeance, will be published in 2025 by Dutton Books.

A native of Pennsylvania, he now lives in Princeton, New Jersey.

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Praise for The Unknown:

“Sager spruces up well-worn genre tropes with aplomb…Sager’s many fans will walk away satisfied.”
—Publishers Weekly

“There are some authors who are an immediate yes regardless of what the book entails. Riley Sager is one of those authors…This is Sager’s 10th novel, marking a huge milestone for the horror mastermind.”
—Parade

“Atmospheric, eerie, and exactly the kind of unputdownable summer thriller that makes you want to stay up way too late.”
—Scary Mommy

"Defined by the full-throated plot twists that Sager has become known for, The Unknown uses the…the 'cursed movie' subgenre to begin conversations about trauma, womanhood and the corrupting cost of fame.”
—New York Times Book Review

“Whether you know him as 'The King of Plot Twists' or 'The King of Thrillers,' Sager’s 10th novel is definitely one we’ve all been keeping an eye on…The Unknown is more than worth the wait.”
—Parade

"Once again, Riley Sager has combined the thriller genre with the supernatural in a way that no one else has so successfully since Stephen King."
—BookTrib

"A shoe-in for one of our most anticipated reads of the year.”
—Fangoria

Praise for Riley Sager and His Novels:
The latest dependable airport bookstore grab and name in summer suspense.”
—The Chicago Tribune

“Sager is a master of the twist and the turn.”
—Rolling Stone

“[Sager’s novels are] all creepily atmospheric, easy to read without being fluffy, and fun as hell.”
—Vulture

"Suspense master."
—USA Today

"With a Vengeance is a locked room thriller at its best! Nonstop suspense with twists and turns that will leave your head spinning!"
— #1 New York Times bestselling author Freida McFadden on With a Vengeance

“Sager is a master of twists, and he delivers plenty of them here. The novel is also full of ’90s nostalgia, but the things stalking the backyard and the mysterious institute hidden in the nearby woods are what make this a gripping read.”
—New York Times Book Review on Middle of the Night

At the top of his game. Sager delivers a thriller so tautly written, so tightly constructed, that readers will emerge from the book breathless and in a mild state of shock. With this book, Sager has committed an act of brilliance.”
—Booklist on With a Vengeance

“Sager’s Middle of the Night is a twisty mystery with a touch of the supernatural, but it’s also about the complexities of friendship, those fleeting but overwhelming feelings from growing up and coming to terms with profound grief.”
—USA Today on Middle of the Night

“A clever and fun mashup of Agatha Christie’s And Then There Were None and Murder on the Orient Express. Sager wields a deft hand in bringing all the elements together into a rip-roaring, tension-filled tale of greed, murder, and revenge. Enjoy the ride on the Phoenix.”
—David Baldacci, #1 New York Times bestselling author of Strangers in Time on With a Vengeance

“Pure escape . . . A voyeuristic page-turner. After I read it, I dove for more Sager: luckily he has five others, bestsellers all.”
—The Boston Globe on The House Across the Lake

Riley Sager’s The Unknown is a tense, atmospheric thriller that blends a locked-island mystery, psychological suspense, supernatural horror, and the unsettling world of filmmaking. The novel moves between 1926 and the present day, connecting two groups of people separated by a century but trapped in remarkably similar circumstances. At the heart of the story is Marin Keane, a struggling actress who finally receives the career-changing opportunity she has been waiting for—only to discover that the role will take her to one of the most mysterious and dangerous places in Vermont.

A hundred years earlier, five women disappeared from New Avalon, a remote island in Vermont’s Lake Faraday. The island had been home to a small commune of spiritual mediums who believed they could communicate with the dead. One night, after a séance, the women vanished. Their bodies were never found. The only physical evidence left behind was deeply disturbing: five dresses were discovered hanging from the branches of an enormous oak tree, one dress for each missing woman. Some people believed the women had escaped voluntarily; others suspected murder. But the most popular explanation came from the diary of Daisy Rue, one of the missing women. Her writings suggested that the séance had summoned a supernatural force that subsequently took the women away one by one.

In the present day, filmmaker Ronan Peters decides to turn this famous mystery into a major motion picture. Marin is astonished when she is cast as Daisy Rue. Until this point, her acting career has been painfully modest, and she sees the film as her opportunity to prove that she belongs in the industry. The production also includes several far more experienced performers, among them the legendary Violet Wright, whose presence intimidates Marin almost immediately.

Ronan's approach to the film is unusual. Rather than simply filming on a soundstage, he wants the actors to experience New Avalon themselves. The cast travels to the island for a week of preparation, wearing period clothing and living without the conveniences of modern technology. There are no phones or internet connections to provide reassurance or an easy escape. Even more unsettlingly, the group participates in séances so that the actors can understand the spiritual practices of the women they are portraying.

From the beginning, Marin feels that something is wrong.

New Avalon is beautiful, but its beauty is inseparable from its isolation. The island feels cut off from ordinary life, and the old buildings and traces left by the former inhabitants create an atmosphere of quiet menace. Strange noises begin disturbing the cast at night. Mysterious symbols appear around the island, including protective-looking markings associated with the spiritual practices of the original commune. Marin also begins experiencing disturbing visions connected to her dead sister, Molly, whose death has left Marin carrying a painful burden of guilt.

The novel becomes particularly effective when the present begins to imitate the past.

The cast members are playing characters based on the women who disappeared in 1926, and gradually the events surrounding them begin to resemble the events described in Daisy’s diary. A health emergency leaves the group stranded, making escape increasingly difficult. Then someone disappears.

At first, the others attempt to find rational explanations. Perhaps someone is trying to sabotage the film. Perhaps a member of the production is playing a cruel practical joke. Perhaps there is an unknown person hiding somewhere on the island. But these explanations become harder to accept as more people vanish. The disappearances begin occurring in the same general sequence as those described in the historical mystery, and once again clothing is left behind.

Marin consequently becomes the person most determined to understand what happened in 1926. Her connection to Daisy is particularly important because she is not merely playing the woman—she is reading the diary and gradually discovering how closely her own circumstances resemble Daisy’s. The diary sections give the novel a second narrative voice and allow the reader to experience the original mystery alongside the present-day one. This structure creates a disturbing sense that history is repeating itself rather than merely being reenacted for a movie.

As Marin investigates, she becomes increasingly suspicious of everyone around her. The isolation intensifies ordinary tensions within the cast. Ambition, jealousy, professional insecurity, personal secrets, and questions about who can be trusted all become more important. Marin herself is particularly vulnerable because she is the least established actress in the group. She has everything to gain from the film, but that also means she has something to lose. Her desire for success makes her question her own judgment: is she genuinely uncovering something sinister, or is fear beginning to overwhelm her?

The supernatural explanation remains deliberately uncertain for much of the story. The characters repeatedly encounter things that seem impossible, yet there are always potential human explanations. This ambiguity is central to the novel's suspense. Sager makes the reader move back and forth between two possibilities: perhaps New Avalon really is haunted, or perhaps someone is carefully manipulating the cast into believing that it is.

Eventually, the investigation exposes secrets surrounding the original disappearances and the people involved in the present-day production. The final portion shifts away from a straightforward ghost story and becomes more complicated, involving hidden motives, personal grievances, manipulation, and revenge. The apparent supernatural mystery is tied to human behavior and long-buried wrongdoing, giving the novel the kind of reversal Sager frequently uses in his thrillers.

Marin's journey is therefore not simply about surviving a haunted island. It is about learning how easily stories can be constructed, manipulated, and believed. The movie itself is an interpretation of an old mystery, while the diary is another interpretation of what happened. Marin gradually realizes that neither version can automatically be trusted. The truth lies somewhere beneath the stories people have been telling for generations.

By the conclusion, the mystery of New Avalon has been transformed from a simple tale of five women supposedly taken by a supernatural force into a much more complicated story about deception, exploitation, trauma, and revenge. The island's greatest danger is not necessarily the unknown supernatural presence that everyone fears. Instead, the novel suggests that human beings can be frightening precisely because of the stories they create and the lengths they will go to in order to control those stories.

Ultimately, The Unknown is a novel about fear, performance, and the uncertain boundary between truth and fiction. Marin begins the story desperate to become an actress, but on New Avalon she discovers the terrifying difference between pretending to experience danger and actually experiencing it. Her greatest challenge is not simply identifying who is responsible for the disappearances; it is learning when to trust what she sees, what she remembers, and what other people tell her.

The result is an eerie and claustrophobic thriller in which a century-old mystery refuses to remain in the past. Whether read as a ghost story, a closed-circle mystery, or a psychological thriller, the novel's central question remains haunting: what if the most dangerous thing about the unknown is not what we cannot see, but what we believe without understanding?