Published in December of 2020, Sarah Pearse’s The Sanatorium is a psychological thriller set in a luxury hotel in the Swiss Alps. It is a locked-room thriller in which the protagonist is tasked with solving a string of murders taking place in the hotel while on a trip to celebrate her brother’s engagement. The book tackles issues such as mental illness, childhood trauma, and sexual assault. The Sanatorium is the first in Pearse’s forthcoming Detective Elin Warner series.

Plot Summary

Protagonist Elin Warner is a young police detective from the UK, who with her boyfriend Will Riley has gone to Switzerland to celebrate her brother Isaac’s engagement. Isaac’s fiancée, Laure Strehl, works at Le Sommet, a hotel in the Swiss Alps that was built on the site of an old sanatorium where tuberculosis patients were once treated.

In the prologue, Daniel Lemaitre, the hotel architect, is accosted by a masked assailant while leaving the unfinished hotel site. His disappearance is downplayed, so as not to sour the hotel opening. Two years later, Isaac’s fiancée Laure is working at the hotel as an assistant manager, and the pair decide to invite family and friends to Le Sommet to celebrate their engagement. Elin and Will arrive a few days before everyone else, but a snowstorm looms, pummeling the mountain resort. Will tries to enjoy their trip, but Elin has a sense of unease that she can’t shake.

After Laure goes missing, an avalanche traps a few guests and members of staff in the hotel. One of the hotel employees, Adele, turns up dead in one of the pools, and Elin must investigate on behalf of the local police. Elin’s suspicions land on Laure when CCTV proves that she is still alive and hiding somewhere in the hotel. She receives a mysterious message from Laure asking to meet at the penthouse, but when Elin goes to meet her, Laure is already dead in the lift. Shocked by Laure’s murder, Elin begins to examine the body for clues, but she is also attacked by a masked assailant, just like the one who killed Daniel Lemaitre and Adele. Will rescues her, scaring off the killer.

Will and Elin overhear the hotel owner, Lucas Caron, and his sister Cecile having a suspicious conversation in the stairs leading from the penthouse. She confronts them about it, and Cecile reveals that the police found Daniel Lemaitre’s remains, and that Lucas didn’t want her to know. When Margot, the spa receptionist, goes missing next, Elin springs into action to find her before the killer strikes again.

Elin and Will find Margot in the maintenance room, but she attacks them, revealing that she took part in the murders because her relative was tortured at the old sanatorium, where the hotel now stands. She stabs Will, nearly killing him, and escapes. As Will recovers, Elin confronts Isaac because she believes that he killed their brother Sam, but he reveals to her that she had watched Sam fall and simply blocked it out. The revelation rocks Elin, her guilt over not helping her brother consuming her. She realizes that she has to find Margot to avenge Laure and Will and to prevent her from hurting anyone else.

From the archive room, Elin and Lucas find a secret tunnel under the hotel. They search the tunnel and find that Margot has been tortured to death there. Lucas leaves Elin in the tunnel, locking her in, and Elin assumes he’s the killer. She texts Isaac, asking him to come rescue her from the archive room, and when he does, she tells him that Lucas is the killer. She asks Cecile to let her into Lucas’s office, and she finds a black mask locked in a cabinet. Cecile expresses disbelief, but as soon as she leaves, Elin smells chlorine on the mask, alerting her to who the real killer is.

Cecile, an avid swimmer, is the killer. Elin finds her near the pools, holding Lucas hostage. She planned the murders in a plot to seek revenge against Daniel Lemaitre for sexually assaulting her as a teenager and against all the people who she felt failed her in some way. Elin knocks her into the pool to stop her from killing Lucas, but she pulls him in with her. They struggle, and Elin finally jumps into the pool to save Lucas.

After the whole ordeal, the Carons are both arrested, and Elin’s relationships with Isaac and Will are strengthened. She returns with Will to the UK, but a mysterious man watches as they ride the funicular away from the mountain.