Deep Dark: A Cassia Thorne Mystery by Zohra Nabi – Spoiler-Free Book Review

Cassia Thorne makes her way in Victorian London selling ballads by day and confined to Fleet Prison by night. When rumours swirl of children been taken off London’s streets, she decides to investigate. With help from a young pickpocket, Teo, and her father’s question lawyer’s assistant, Felix, she discovers a sinister movement that encases all of London’s highest-ranking professions, involving mysterious men and a beast in the city's underground tunnels. Cassia must unravel the mystery and rescue the children before the lives of her and those around her fall into unsafe hands... or tentacles…

Deep Dark: A Cassia Thorne Mystery by Zohra Nabi is released on 27th March 2025 by Simon & Schuster.

Cassia is a divine protagonist. Full of heart, gall, drive, morality, talent, creativity, and more, she is one of those protagonists that, even when she does wrong, you’re behind her completely because you can see her good intention. Between dealing with her own childhood past, her family dynamic of her father in the Fleet, trying to make a career for herself, and then getting embroiled in this mystery, it takes a special type of lead to guide a reader through that and Zohra Nabi has made sure Cassia is just that!

Teo has my heart completely. With a similarly part-Italian heritage and a musicality about him, I can’t help but warm to him immediately and I rode the wave of his storyline committedly throughout. Between the The Kingdom Over The Sea series and now the Cassia Thorne series, Zohra Nabi continues to shine in her ability to deliver as well rounded secondary characters as her protagonists without falling into any tropes or ‘sidekick’ stereotypes. I adore Teo, and Felix, and Elisabeth, and even the antagonists too. Secondary characters dazzle equally in Deep Dark.

Narrative-wise, there’s a great deal of praise to be heaped on the author here, as there was an exceptional balance of reveals that older (11–12-year-old) readers would get whilst also those complete right turns that even myself, as an adult, couldn’t have imagined. I think that’s important in mystery writing and whodunnits as, especially children, they want to feel like they can work out the mystery with the protagonist too. There’s been a few whodunnits of late that have felt like a collection of right turns and that can be off-putting. Therefore, the ability to parallel those alongside each other throughout the whole novel isn’t easily done and I was thrilled with it!

Emotionally, this novel took me on an absolute journey and is the third book this year that has made me cry in public! I would never dream of saying what it was, but I had to really restrain myself from the ugly sobbing I wanted to do that would’ve got me kicked out of the coffee shop I was reading in. I also laughed from the ribs, smiled like the Cheshire Cat, got angry, and came away from some plot points with a lot to think about!

I am ecstatic that Deep Dark is the first Cassia Thorne book, and I truly hope this is the start of a series that lasts for plenty books to come. For a long time, I’ve been waiting for a detective who I believe could lead a longstanding series like the young detectives of decades past and Cassia is that protagonist. If you haven’t, make sure you go and preorder now and in the meantime, make sure you check out The Kingdom Over The Sea and The City Beyond The Stars because they’re marvellous too…

There is something wonderful about holding physical book in your hands and turning the pages, allowing the story to seep into you, but... there is also the lure of NetGalley which allows bloggers like me to read books before they're available in print. When I discovered that Deep Dark was on NetGalley, I hesitated for all of 5 seconds before hitting the 'read' button and diving in.

Deep Dark is very different to the Kingdom series but is just as wonderful. Upon opening the book, readers are transported to Victorian London and to the plight of the many homeless children forced to make a living on its streets. For Cassia, her life changed when her father's shipping business went bankrupt and now she and her father live in Fleet Prison, having made the long journey from India in a failed attempt to sort things out. Whilst she is allowed to wander free during the day, her father is confined to their squalid apartment. As a result, Cassia has no choice but to fend for herself, making money by selling ballads and by teaching the piano, all in an attempt to escape to a better life. But strange things are happening and children have been going missing all summer. With nobody willing to help, Cassia and her friends, Felix and Tao, decide it's up to them to save the missing children. However, what they uncover proves far more sinister than they could have ever imagined and saving the children becomes more urgent than ever.

Where the Kingdom duology (you can read my reviews here: The Kingdom Over The Sea The City Beyond The Stars ) transports readers to the rich and vibrant world of Zahaira, Deep Park brings to life the gritty reality of so many street children who were forced to live on the streets of London, stealing food and making money any way they can. Zohra's descriptions are vivid and brings the streets of London to life for readers who will find themselves visualising the city as they read.

Cassia is a fiercely independent and tough character who has a heart of gold; after all she's had no choice. She is fiercely loyal to her friends and desperate to do the right thing. Life has been far from easy for her and the move from India to London must have been difficult enough but to then have to grow up in prison and fend for herself, it's a wonder she isn't full of spite and bitterness. She is a truly wonderful character, full of resilience and gumption in the face of adversity - readers are going to love her. Along with her friends, Tao and Felix (characters who couldn't be more different from each other), she is determined to do right by the street children of London, and nothing will stop her.

At its heart, Dark Deep is an unputdownable adventure that will grab readers from the very beginning. I stayed up way too late last night reading it as I just couldn't put it down and I know that it's going to be a huge hit when it publishes on the 27th March. The Kingdom books showed us how well Zohra writes and Deep Dark firmly establishes her as a must-read writer. There are a select group of authors whose books I will read without even looking at the blurb and Zohra has firmly established herself in that group. If you only pre-order one book this year, make it Dark Deep - I promise you won't regret it. I'm now very much looking forward to getting my hands on a physical copy as I know how much my class are going to love it.

Cassia Thorne lives in Fleet debtors’ prison with her father, spending her days wandering the streets of Victorian London, fending for herself and making a few pennies selling ballads and giving piano lessons.
When the younger brother of one of her friends disappears without trace, she is determined to help with the search. She teams up with friends Teo and Felix and they discover a sinister plot involving city elders and a roaring beast whose home is deep underground. Cassia, Teo and Felix are in a race against time to unravel the mystery and rescue the missing children.
Cassia is a wonderful protagonist who is bold, resourceful, resilient and determined to champion the cause of the street children of Victorian London. Teo and Felix are the perfect secondary characters, each with an interesting back story and each having skills and knowledge which complement those of Cassia.
The descriptions of Victorian London are so vivid and compelling, young readers are sure to look for clues to London’s past next time they visit. The mystery which is central to the plot is complex enough to be interesting whilst still allowing readers to work out the clues alongside Cassia and her friends.
Deep Dark is the first in a series and I can’t wait to read Cassia’s next adventure. Meantime, take a look at Zohra’s other books “The Kingdom Over the Sea” and “The City Beyond the Stars” because they are wonderful too.

Children are going missing from the streets of London, and Cassia Thorne refuses to just stand by and watch.

Nabi’s writing is immaculate; it carries you along with it, poetic and deft.

Our protagonist Cassia is well-rounded—determined and ambitious but not without her anxieties. She’s immediately likeable, and you root for her the whole way through.
The supporting cast of characters was delightful—Teo was my favourite!

The setting is perfectly sketched, capturing the exciting bustle of the city, but not shying away from the grimness of life on the streets. I also loved how it didn’t neglect the diversity that existed in Victorian London.

I love a story about institutional corruption; I love a secret river. I love a MG book that isn’t afraid to get a little dark, but stay hopeful. Honestly, a perfect book that I believe will inspire a new generation of young readers to stand up for what is right.

I’ve said countless times that I’m a sucker for a gorgeous cover and when this one popped up in my Twitter feed a few days ago to say it had been added to NetGalley and I then clocked the name of the author, it was a no brainer as to whether or not to request it. Swiftly approved alongside several other kidlit-loving friends, I have to admit to feeling rather smug that I was able to dive straight in while they had to wait patiently until the end of their working weeks to pick it up.

A very different story from The Kingdom Over the Sea, Zohra Nabi’s debut read, this is another accomplished fantasy that is just the start of a new series for middle grade readers. Set against the backdrop of a brilliantly-researched 19th century London, it again features a bold, brave and intelligent heroine and is one that I know is on many kidlit fans’ lists of must-reads for 2025.

For 14-year-old Cassia, hanging around outside pubs is something that she knows is not respectable but is a necessary evil if she is to earn enough to feed herself and her father. Entering The Cheshire Cheese, she meets up with Josiah Hawke and informs him that she no longer wants to sing for pennies but instead write the ballads that make him his living. Persuading him to take her song, she exits the pub a little better off and heads to Smithfield where the Bartholomew Fair is taking place, visiting a friend before going to speak with Teo, from whom she learns wonderful stories to weave into her ballads.

Returning home to the Fleet Prison where she and her debtor father live, Cassia resigns herself to helping him with his endless letters and dreams of a future free from the shame of her current circumstances. Heading to bed, her sleep is disturbed – as it has been for several months – by a recurring nightmare in which she runs for her life from something that is coming after her. Waking the next morning, Cassia heads out and after attending to some business finds her way back to Smithfield where she discovers that her friend’s brother has vanished – just the latest of many children who have done so.

Promising to help find him, Cassia is soon drawn into a mystery and together with new friend Felix searches for clues, uncovering a shocking scheme behind the disappearances. Pitted against a network of powerful adults working within Great Britain’s capital, can Cassia work out how their plans are linked to her nightmare, and if she can will it be in time to prevent it becoming real?

Hardworking and almost entirely self-reliant, Cassia is a heroine for whom young readers will feel an enormous empathy. Having lost her mother at a very young age, her remaining parent is seemingly oblivious not just to his daughter’s needs but her not inconsiderable efforts to ensure that the two of them do not starve to death. An old head on young shoulders, Cassia refuses to be broken by her situation but dreams of a better life, like so many people do, but realistically with very little hope of ever escaping from the Fleet. For today’s children, who will be aware that poverty is still a sad reality, the descriptions of Cassia’s home, the workhouse and those who live alongside her will serve to make them love her all the more and cheer her on as she tries to solve the mystery of just what is happening around her.

The first in a new series, this doesn’t finish on a cliffhanger as such but does end with Cassia’s future very much up in the air – a situation that is bound to have many readers keeping a very close eye out for her next adventure once they’ve finished this one. Before that, my thanks go to publisher Simon & Schuster and to NetGalley for my virtual advance read. Deep Dark publishes 27th March.

I really loved Zohra's book The Kingdom Over the Sea, and its series, and so I jumped at the chance to read this new book.

I mean, for starters, it has a map! And a beautiful cover - let's stop kidding ourselves, we totally judge a book by its cover. It also has illustrations. I am a big fan of illustrations in books and I wonder if that's one of the reasons I love reading children's books so much, because it's rare that you get illustrations in an adult book.

It's got that right amount of terror to entice children but not frighten them silly. And it's got enough heart to entertain this new 32-year-old.

It's got a mixture of everything; yes it's a children's book, but it has fantasy, magical elements, adventure, detective, a little horror.

I feel the same way about Zohra's books as I do about the books I read as a kid, such as The Goosebumps series. They've got enough about them to really entertain readers of all ages and I think younger readers will definitely enjoy them.

This is completely different to Zohra's previous series. Whereas that was set very much in a fantasy world, this is set in London. Yes there is magic and mystery within it, but it is very much set in a recognisable, if old, London.

Cassia is our main character. She's in her early teens but she's clearly had to grow up quickly and that's made her smart and strong. Which helps her a lot in this book. There are lots of other characters, children and adults, goodies and baddies, mystical and recognisable, and they all work to further Cassia's story.

I think overall I preferred her previous books, but that's because I was fully swept up in the magic of it. This book is grittier and darker, which is great to read but completely different to what I was expecting. It's a harder read as well due to some of the topics touched upon, which I also wasn't expecting for a book aimed at such a young reader.

It was also a lot slower to get going than I expected. I mean, let me contradict myself here, I'll say it does start with a bang, but I was expecting a bit more whimsical-ness earlier on. I understand a scene has to be set, and it's fine as it is, but I wanted more magic a little bit earlier.

It doesn't end on a cliff-hanger, which I thought it would do, but it's a good ending. It wraps up everything from this story but teases the possibility of more. I think the characters' journeys - particularly Cassia's - are really well developed and overall I think it's well paced (for the most part), with interesting characters, it's scary but not too much, it's fun and magical, with heaps of history in it.

I do believe this is the first in a series and so it'll be interesting to see how she follows it up.

What don’t I love about this book. It is everything I want in a story. Truly a masterpiece. I cannot wait to preorder this story. I loved it so much. I would highly recommend it 10/10