This is the tenth novel in the excellent Inspector Joona Linna series but can be read as a standalone. I would recommend starting with the first novel to get a complete understanding of the wonderful characters and a feeling for how these novels are so dark, intense, gripping and on the edge.
This story starts with a young man found sleeping at a horrific crime scene and then takes you on a fast paced ever twisting storyline that will keep you page turning.
I highly recommend this book and the complete series. Hope it is not to long for the next one

This was another fascinating story in the Joona Linna series of books. Each can easily be read as a standalone thriller but I found my enjoyment increased dramatically after reading them all. After discovering this series with book 8 I then went back and read them all before continuing with the series further, it was worth it!

This book has quite a sedate pace which is a bit of a relief with how gory the crimes are so there is time to recover between each bloodbath. The narration makes it difficult to put down for me as I wanted to know who was behind all of it and to try to understand why it was happening. I admit to feeling a little shock when it was revealed but with that explanation it all made so much sense of even those things I had thought were going to be just background noise to the tale. This book tells a fabulous story from start to finish in a very easy to read style, it was a very enjoyable read.

I am always drawn to the darkness of Scandi-noir, and Lars Kepler’s Joona Linna series delivers that darkness in full force.

The Sleepwalker is brutal, chilling and impossible to look away from. It opens with an arresting and grotesque scene in a winter-closed campsite, setting the tone for a tense and unrelenting investigation.

Seventeen-year-old Hugo Sand is found asleep beside a severed arm, covered in blood, with no memory of what happened. His rare sleepwalking condition adds another layer of uncertainty – is he a killer, a witness or something in between?

As Joona Linna teams up with hypnotist Erik Maria Bark, the investigation spirals into a sleepless hunt for a serial killer who is far from finished.

The combination of horror, psychological suspense and personal trauma makes this an intense read. Kepler’s pacing is razor sharp, the atmosphere is oppressive, and the twists keep the tension high right until the end.

Read more at The Secret Book Review.

A young man is found asleep at a horrific crime scene. Is he the perpetrator or just and innocent witness? Detective Joona Linna has to investigate the phenomenon of sleepwalking. However it is clear the boy cannot recall what happened so hypnosis is employed. As Hugo regresses into his nightmares, so the body count rises.
Lars Kepler is the pseudonym of a writing partnership and this is another excellent Scandi-crime novel from the team. The murders are suitably gruesome and the psychology elements clearly explained. Yes, there's the gratuitous sexual perversion side-plot but it's not overplayed. All in all a very enjoyable addition to the canon

The Sleepwalker by Lars Kepler is the tenth book in the excellent Joona Linna Series and I have only read a few of these books and everyone I have read has been excellent. I love the way Lars and his wife writes, their books are so dark and I am drawn to the darkness of Scandi-noir, They are always cleverly written from start to finish, they just draws you into the book especially as it will have you guessing who the Killers or Killers are to the very end!

Superb read! But don't start to read their books as you are about to go to Sleep! You will have nightmares! or you may not be able to put their book/s down, they are so addictive!!!!

I’m drawn to the darkness of Scandi-noir, and Lars Kepler’s Joona Linna series is darkness itself. The latest novel in the Joona Linna series, The Sleepwalker combines horror, personal trauma, and psychological suspense.

The opening setting is a desolate, closed campsite outside Stockholm, in the depths of winter. Responding to an emergency call, police enter one of the furthest caravans and are met with a scene straight out of a nightmare. Walls, floors, and furniture are drenched in blood, and a body lies brutally murdered. Amid the carnage lies a teenage boy, asleep, using a severed arm as his pillow. The boy is Hugo Sand, the seventeen-year-old son of bestselling writer Bernard Sand, who suffers from a rare form of sleepwalking, induced by his nightmares. Questioned by police, Hugo insists he remembers nothing. Joona must try to open up this boy’s memory while pondering the question ‘Can a sleepwalker kill without ever waking up?’

Lars Kepler’s style is unmistakably tense. Short chapters, cliff‑hanger endings, and alternating perspectives kept me turning the pages. The tone is cold and clinical. The descriptions of blood and death are pretty gruesome yet never gratuitous (though I’m less able to say that in respect of the later sex scenes). It’s the kind of visceral horror that stays in your mind well after the book is closed.

Joona Linna is a detective peering into the shadows, finding not just a killer but human darkness. In The Sleepwalker, he’s weary, but his determination is as fierce as ever. The first half of the book is dominated by Hugo’s experiences and his visits to a sleep clinic. Joona doesn’t really come into his own until later in the book.

Joona asks his old friend Erik Maria Bark to retrieve memories from Hugo’s mind. Erik’s role as a psychologist‑hypnotherapist is perfect for Hugo’s blank recall. These scenes were especially tense with Erik Maria Bark gently coaxing fragments from a teenage mind, peeling away nightmares to find the truth. Joona and Erik’s partnership works because Linna remains the hunter, methodical and stubborn, while Bark’s clinical precision and psychological insight open windows into dark memories. Every new memory revelation shifted my suspicion.

Saga Bauer, Operational Superintendent at the Swedish Security Service, is notably absent in this case, though Joona wants her to return to work. Joona without Saga feels incomplete—her presence and emotional ballast have anchored previous books. Saga’s absence enhances the feeling of isolation in this story.

Hugo is drawn sympathetically: as the son of a famous writer, he is subject to public scrutiny even before his sleepwalking nightmare. Hugo’s guilt, shame, and vulnerability are tightly wound around his father’s fame and expectations as much as around the physical horror of the crime scene.

The trauma within the Sand household simmers with tension. Hugo’s father is confused and fearful. He’s torn between defending his son and confronting the horror Hugo is implicated in, with no idea whether Hugo is a perpetrator or a victim. The novel explores grief, denial, and the weight of parental failure. We also see Hugo’s relationship with his girlfriend, Olga, a strange woman who is helping him to find his birth mother.

The body count mounts, and each is more brutal than the last. Clues are scarce, and evidence is both forensic and psychological. The gore increases, and there’s a sense that the killer is taunting police. A vivid hair is found at scenes, bodies are posed in sleeping positions; all these forensic breadcrumbs make the a procedural case, while Bark’s hypnosis technique digs ever deeper.

Verdict: The Sleepwalker isn’t subtle. It doesn’t aim to be quiet comfort reading—it’s sleepwalking into nightmare territory; forensic terror mixed with psychological wreckage, tied up in Linna’s unstoppable drive to solve the case. The Sleepwalker is bleak, engrossing, and fascinating. Kepler leads us through horror and hypnosis, crime scenes and shattered memories. This is Scandi noir stripped bare, blood‑soaked in grief and nightmares.

I love this series of books. This was gripping if not a bit gory. Love returning to familiar characters.

The enjoyed the fractured relationships, the buried grief, the intimate cost of justice. This isn’t just a crime thriller: it’s an exploration of vulnerability, and the ways we carry guilt, even when we can’t quite trace its origin

This was such an exciting premise for a book, if you witness a murder while sleepwalking, will you remember it when you wake up? As the deaths mount Jonna Linna has only sleepwalking Hugo as his ‘witness’ to help him put a stop to the vicious murderer. Gruesome, graphic and highly entertaining I thoroughly this latest instalment in the series. Thank you to Netgalley for the advance reader copy.

Love love loved it!!! Another fantastic book in the Joona Lina series.
I’ve followed this series from the beginning and it never disappoints. The was a really good book, fast paced and gory - just how I like it! This has a really clever story line and I would never have guessed who the murderer was.
I would liked to have seen a bit more of Joona and Saga’s lives but I think that’s just because I love them and love their storylines aside from the main mystery in each book.
The only downside for me was the sex scenes, it was a bit much for me but I am a bit of a prude!

A huge 5 stars for me!

When a man is found brutally murdered in a blood-soaked caravan, seventeen-year-old Hugo Sand is discovered asleep beside the body. Suffering from a rare sleepwalking disorder, Hugo remembers nothing. Detective Joona Linna enlists hypnotist Erik Maria Bark to uncover the truth—unravelling a chilling hunt for a rising serial killer.

Kepler masterfully blends forensic detail, psychological suspense, and relentless pacing. The novel’s strength lies in its gritty portrayal of human evil and the emotional depth of its characters. Fans of Nordic noir and dark crime fiction will find The Sleepwalker a gripping, disturbing, and unforgettable read. Recommended

Thank you to NetGalley and the publishers, Zaffre, for an ARC in exchange for an honest review.

When a young man is found sleeping beside a dismembered body he is arrested for murder. In the course of the investigation, it is proved that he didn't do it, but that he could have vital clues to who did.
Joona Linna and the team are tasked with tracking down this killer before more bodies are found. Not an easy task. The only forensic evidence is a blonde hair found at the scene.
Hugo, the young man first arrested, is the son of author Bernard Sands. He and his girlfriend want to help the investigation as much as possible. They allow Hugo to be hypnotised at the sleep clinic to see if his memories can be recovered.
An interesting and page turning thriller which I absolutely loved.

The Sleepwalker is my first read by this author and it didn't disappoint in any way at all. I like Scandinavian crime books and from the blurb thought that this read would be for me and it certainly was. The authors story writing is good and engaging, it is very descriptive at times and quite graphic which I liked, although this may not be for everyone and depends on how gory you like your crime reads to be. The plot is well thought out and when Hugo witnesses a murder whilst sleepwalking the Police are desperate to know what he saw and have to work out what is real and what isn't. I really liked Linna and Agneta and although I didn't take to Hugo initially he began to grow on me the more I read. There is a lot of tension and suspense in the story which adds so much atmosphere and really gives the characters good depth. I felt Linna didn't feature much in the first half of the story - I'm more used to the investigating officers having more of a presence in the story. Nevertheless this is still a good and enjoyable read, it didn't quite wow me though and had an ending that surprised me to say the least. I'd like to see what is in store next for Linna and will look to read the previous books in order when I can.

3.5 stars

I love a Joona Linna thriller and this one is my favourite so far.
Hugo is a sleepwalker. Whilst sleepwalking one night it appears that he may have witnessed an axe murder at a caravan park. Events spiral and soon Linna has a serial killer on his hands.
This book is very cleverly written and you won't want to put it down. Graphic in places, but worth it!

Hugo Sand is a sleepwalker, it has caused a few issues over the years but when he is found in a deserted camping site using a human arm as a pillow, then the real trouble begins.

This book is not for the faint hearted, some of the scenes are quite graphic so may not be for you if you have a nervous disposition. Saying that, I really enjoyed it, story flowed, interesting characters, and I was mentally preparing my review at one point, had it in my head that I would say too many clues, and it was obvious etc etc, boy was I wrong about that!

Couldn't put it down, highly recommended.

This chilling thriller explores the terrifying idea that someone can sleepwalk and commit murder but remember nothing.The chapters are short yet filled with tension where danger lurks around every corner.
Parts are deeply sinster others brutally graphic this isn't a book for the faint hearted as it really gets under your skin.
This Scandinavian noir really gives the reader what they want as long as you're ready to strap yourself in for the ride.
Thanks to Netgalley and Bonnier Books UK for the Arc

Thank you NetGalley and Bonnier Books UK for this eCopy to review

The Sleepwalker is everything I want in a Nordic thriller dark, disturbing, and utterly relentless. From the blood-soaked crime scene in a deserted Stockholm campsite to the psychological depths of trauma and memory, this novel gripped me from the first page and didn’t let go. It’s a story about sleep, secrets, and the terrifying things we’re capable of when we’re not even awake.

🧠 Plot Summary
When police respond to a late-night emergency call at a closed campsite, they find a scene straight out of a nightmare: a man brutally dismembered, blood everywhere, and a teenage boy, Hugo Sand sleeping beside a severed arm. Hugo, the son of a famous author, suffers from a rare form of somnambulism triggered by nightmares. He remembers nothing.

Enter Joona Linna, who enlists hypnotist Erik Maria Bark to unlock Hugo’s memories. But what begins as a search for truth quickly spirals into a hunt for a killer who is not only active but escalating. As Joona digs deeper, he uncovers a chilling pattern and realizes that Hugo may not be the only one sleepwalking through horror.

🔍 What Worked

The Premise: The idea of a sleepwalker possibly committing murder is both horrifying and fascinating. Kepler uses it to full effect, blending science and suspense.
Joona Linna: As always, Joona is a compelling lead—relentless, intuitive, and haunted by his own past.
Pacing: The short chapters and cliff hanger endings make this a compulsive read. I flew through it in two sittings.
Psychological Depth: The exploration of sleep disorders, memory repression, and trauma adds a rich layer to the procedural elements.
Atmosphere: Cold, clinical, and claustrophobic—Kepler’s Sweden is a place where danger lurks in every shadow.

Final Thoughts
The Sleepwalker is a chilling, high-stakes thriller that blends forensic detail with psychological suspense. It’s not for the faint of heart, some scenes are very gruesome and genuinely disturbing, but if you’re a fan of dark crime fiction, this one’s for you.

I had actually just finished the hypnotist so this was perfectly timed to continue onto the sleepwalker and wow! These books have such a deep hold on me. They're so cleverly written and the plot is so deep. There are multiple plotlines all intersecting and the actual concept of sleepwalking and the obvious research that has been done into the phenomenon is really interesting to consider in itsself. Brilliantly written, utterly captivating and genius level twists and reveals! A must read

The Sleepwalker (Joona Linna No10) by Lars Kepler
2025 Worcester Blue Crime

The Sleepwalker is the tenth book in the Joona Linna series by crime writing duo Alexander Ahndoril and Alexandra Coelho Ahndoril.

In The Sleepwalker, the husband-and-wife writing duo known as Lars Kepler once again provide a gripping instalment in the Joona Linna series. This is a dark, sometimes disturbing thriller that is a fine example of Scandinavian noir.

A man is discovered butchered inside a closed campsite outside Stockholm. The walls and floors are covered in blood and close by a teenage boy is found asleep, curled up beside a severed arm as if it were a pillow. The boy is Hugo Sand, son of a renowned author, and he suffers from a rare sleep disorder that may have made him a witness or murderer. A gripping, yet dark opening to the novel which set the tone for the rest of the story.

Detective Joona Linna is assigned the case and brings in hypnotist Erik Maria Bark to help piece together Hugo’s fragmented mind. This is shorty followed by a further murder which leads Joona to think that a serial killer is on the loose.

I thought the hypnotism scenes were particularly sinister and atmospheric. Joona is once again racing against time to solve the case before there are more deaths. The book is very atmospheric, set in cold bleak Scandinavia and an enjoyable read. I thought it was a little drawn out at times but was still glad I read it.

I would like to thank both Netgalley and Bonnier Books for supplying a copy of this novel in exchange for an honest review.

another whip smart instalment by a very smart team. these two keep proving their skill and keep proving just how the magic of writing and thinking of stories together is a true gift to have. but it must take work i always think to get books this good, to get crime back feeling so tight and smartly done. its real. its like you are seeing thought out and planned scenes. you are seeing research. you are seeing as i said a brilliant duo of a writing pair.
there is a reason we like the Scandi noir books and books like this series is one of them.
i felt all the dark and tense moments in this book. the sleepwalking aspect was just so good! it added such a eerie feel to it and the atmosphere continue to become so much part of the reading as we continue through the book to find a incredibly dark killer.
the characters are always described to perfection in these books. Scandi noir books seem to do this in such bright and alive detail. i dont know how they just seem to get it to some beautiful art.
i really enjoyed this book. it went up and up in my enjoyment rating throughout. and i love it when i open a book knowing im in great hands and once again Lars proved it to be true.