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John Decker #4

Grendel's Labyrinth

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A terrifying force unleashed on the Irish countryside.

Under a ruined monastery near the quaint village of Clareconnell, a labyrinth of caves hides a dark secret. The remains of Grendel. Defeated by Beowulf and entombed there by the Danes, he has remained hidden for a thousand years, guarded first by warriors, then by monks, and finally by the villagers themselves.

But nothing stays lost forever.

A team of archaeologists are excavating the monastery and searching for his grave. Because Grendel’s bones may hold the key to a medical breakthrough that could change the world.

When John Decker, newly recruited to the shadowy organization called CUSP, arrives in the Emerald Isle to retrieve the bones, he discovers that there’s more to this idyllic village than meets the eye. For Clareconnell has a dark and shameful past, and now that the caves have been opened, the villagers must pay for their sins…

This is book four in the John Decker series, but it can be read as a standalone novel.

If you are a fan of James Rollins, Douglas Preston, Lincoln Child, and Steve Alten, you will love the John Decker series.

268 pages, Kindle Edition

First published September 30, 2020

846 people are currently reading
299 people want to read

About the author

Anthony M. Strong

36 books307 followers

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5 stars
795 (51%)
4 stars
532 (34%)
3 stars
201 (12%)
2 stars
25 (1%)
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3 (<1%)
Displaying 1 - 30 of 95 reviews
Profile Image for Zain.
1,884 reviews286 followers
June 21, 2024
The Abattoir

John Decker is now a member of CUSP. Which stands for Classified Universal Special Projects. He was requested by Adam Hunt.

They are going to Ireland to look for Grendel, the monster from Beowulf. The monster is a very violent and very vile and vicious creature. He lives in an abattoir.

Decker and Hunt and Rory McKinnon and Sean o’Collum are all very much similar in their respective ways and attitudes.

They think that the archeologists have found Grendel’s remains and that they will soon have them nice and tight.

But the remains turn into a big shock…

Four stars. ⭐️⭐️⭐️⭐️
Profile Image for Marie.
1,119 reviews389 followers
Read
May 28, 2023
Well what to say about this book......

I really hate to "dnf" this book but for some reason as much as I have loved this series so far this book is not pulling me into the storyline. I have been struggling with it for awhile now hoping it would get better but it has been dragging along and I have been waiting for something to literally take off and happen with giving me that "chill factor" that I have come to expect with this series.

This book is doing nothing for me and the more I try to read the story the more I struggle. So I am putting it down as I am not going to keep on muddling through it if I am not enjoying it. Thank goodness the books in this series are all stand alone books so I am not going to be missing anything when I decide to read the next book in the series. Which will be later on down the road as I am not feeling up to reading book five now. I have other books to read. I am not rating this book as I do not rate books I do not finish.
Profile Image for Regina the Constant Reader.
396 reviews
April 24, 2025
⭐️⭐️⭐️⭐️ -Audiobook 🎧

John has agreed to join the CUSP team and his first assignment is in a small Irish village to find the bones of Grendel who was defeated by Beowulf and place there by the Danes. John and the team find more than they’ve bargained for underneath the ancient monastery where monks had kept a secret in the labyrinth of caves that the town is still guarding hundreds of years later.
Profile Image for Donna Thompson.
659 reviews47 followers
October 12, 2020
Reading a new John Decker novel you know right from the start that you're in for a treat. Add in an archaeological dig with a mythological creature and you have the recipe for an entertaining, action-packed thriller. For a series to succeed, the author has to create a recurring character that is appealing, interesting and believable. This series nails it on every level. Decker's team of co-workers are an intriguing group themselves. In addition to the characters, I especially enjoyed the setting in this one. You can't really go wrong with Ireland. Steeped in legend, myth, magic and mystery, it's a prime piece of real estate for the action in this book. Overall, you can't go wrong with this or any of the books in this series. Mixing several genres actually works quite well for these stories and there's something to appeal to everyone. It's a sign of a good book when you finish and are already anxiously anticipating the next. **I volunteered to review a complimentary copy of this book.**
Profile Image for Sudasha.
644 reviews17 followers
January 6, 2022
Not as great as the first few books, but I'll still carry on reading the rest of the series.
Profile Image for Sammie Reads.
1,134 reviews183 followers
July 13, 2024
While this wasn’t my favorite of the series so far, it was definitely really entertaining!!! I love that every book has had a completely different location, all with its own culture and nuances, and this one being set in Ireland only added to the vibe. John Decker, recently hired by CUSP, is on his first secret mission with the agency. They’re looking to uncover the grave and body of Grendel, the legendary beast that Beowulf defeated. Legend says that the Danes brought Grendel to Ireland after they couldn’t kill him, and tired of losing so many men to his ravenous appetite.

But when Decker arrives in Ireland, and people start turning up missing…or dead, he has his doubts as to whether Grendel is actually dead. It turns out, this sleepy Irish town has been harboring a secret for hundreds of years. And one of the many questions that may be answered by the mystery is…why is there no town cemetery? This was medium paced, interesting, and a little thrilling, all things we’ve come to expect from Decker and co. And as a bonus, I didn’t see Astrid’s secret coming, which was a fun treat!
Profile Image for ❀ Crystal ✿ -  PEACE ☮ LOVE ♥ BOOKS .
2,532 reviews308 followers
November 13, 2024
After finally accepting a new position for a secret government organization, Decker is off the Ireland. A group of researchers and archeologists have found artifacts relating to Grendel from the Beowulf tales. Even with his past it takes Decker a while to figure out what is plaguing this small town and why the town has zero cemeteries. Another fun and interesting read that slowly blended with more supernatural elements after the last two books' monsters were explained away. Not sure why it's bothering me so much but at the end of the last book Decker asks his long lost love to marry him and rather than saying No she asks for time. For Decker this is tantamount to a No and he harbors such a grudge over it which is really bothering me as she has a bad past from her last marriage. He even almost cheats on her and it's now making me question his character which I've pretty much enjoyed until now. Hopefully they can work it out or decide to let each-other go once and for all.
Profile Image for Melissa.
740 reviews27 followers
October 19, 2021
Basic plot-search for Grendel’s bones. Ends up being more than that. A completely ridiculous story that was 100% enjoyable. Not believable at all but fun to read.

Not sure how I feel about Decker. He’s been through too much to still be such a skeptic. That is what takes some fun out of the story. If you’ve read the previous books there is no reason he should continue to question the existence of the supernatural world and the horrors created by man.
Profile Image for MRS G .
267 reviews3 followers
March 5, 2023
I thought this book was a great read. In fact my fave so far!

They're easy but intriguing reads, very enjoyable and you don't need to be Einstein to work out what's happening.

Jack the ripper here I come...
Profile Image for Shawn Deal.
Author 19 books19 followers
June 14, 2023
Totally addicted to this series. Ordered another three books in the series. What higher praise than that.
Profile Image for myreadingescapism.
1,273 reviews15 followers
January 19, 2025
Alright, I won't even lie. These aren't that ground breaking, instead of chasing after a serial killer... we're chasing after creatures and you really just can't go wrong.
Profile Image for Teresa.
1,900 reviews33 followers
July 6, 2021
So what exactly does Decker do? Just be there?

I don’t like the John Hunt guy and business, too obviously contrived.

Not as good as the previous books.
36 reviews3 followers
October 6, 2020
Enthralling read!!!

This book is the 4th book in the John Decker series. The previous 3 books had me gripped from the very 1st page to the very last, as did this new book. This series is set in Ireland which is different and a nice change from the usual settings on John Decker's adventures. This book was so addictive and unputdownable, one more chapter then one more. As I was reading it I could feel my heart racing faster in anticipation of .... oh my god what is going to happen next, even I didn't know what to expect. Yet another totally gripping adventure with John Decker, just when you thought he was in for a quiet life ...... this author has sent him on another shocking and terrifyingly trip. Not for the fainthearted, if you like your horror and gore. This author has not disappointed me, but left me thirsty for more of his brilliantly written words. An addictive series. BE WARNED!!!

Looking forward to more from this author.
Profile Image for Thomas.
215 reviews25 followers
September 7, 2021
The marketing on Facebook got me again!

A terrifying force unleashed on the Irish countryside.

Under a ruined monastery near the quaint village of Clareconnell, a labyrinth of caves hides a dark secret. The remains of Grendel. Defeated by Beowulf and entombed there by the Danes, he has remained hidden for a thousand years, guarded first by warriors, then by monks, and finally by the villagers themselves.

But nothing stays lost forever.

A team of archaeologists are excavating the monastery and searching for his grave. Because Grendel’s bones may hold the key to a medical breakthrough that could change the world.

When John Decker, newly recruited to the shadowy organization called CUSP, arrives in the Emerald Isle to retrieve the bones, he discovers that there’s more to this idyllic village than meets the eye. For Clareconnell has a dark and shameful past, and now that the caves have been opened, the villagers must pay for their sins…


What a great story idea. I loved the thought of catching up with Beowulf and Grendel. It would be fun to see what my old friends from high school have doing after all these years.

But alas, the story was a bit on the silly side. I read up right to the very last page hoping that Mr. Strong would explain the reason for the actions that led to Clareconnell's "dark and shameful past".

Never got an answer.



This is my first exposure to The John Decker Supernatural Thriller Series. Mr. Strong is skillful at creating suspense and prompting the reader to keep on turning the pages, (which is why I rated this story 3 stars instead of 2 or even 1) but he left just too many unanswered questions and holes in logic for my taste.

I'll try one more episode before I pronounce final judgement.
Profile Image for Boomer.
394 reviews5 followers
March 2, 2022
I've enjoyed the idea of this series for a long time but I have to be honest and say this is the worst book so far. Loved the idea of doing something based on Beowulf and Grendel, but this is terrible. John Decker is sent by his new mysterious employer CUSP to Ireland to retrieve the bones of Grendel which supposedly have the ability to potentially grant eternal life (it's never explained how this could be achieved). Upon arrival he finds Grendel alive and has to face off against the beast.

SPOILER WARNING *****

Although previous books at least attempted an explanation of their monsters, this one doesn't bother. We just have to accept the fact that somehow Grendel has been living in a cave system under a village for a few thousand years, feasting on the occasional corpse the villagers throw him. Oh, and his thousand year old mother is somehow also an archeologist that has infiltrated Decker's clandestine group. Sure. The author doesn't even try and come up with how this is possible. Grendel's very sensitive to light.... except when he attacks guys with high powered flashlights, or people in lit buildings. It's actually really funny, but I don't think that was the intention.

END SPOILERS ****************

I'm not sure where to go with this series. I love the idea with these Monster of the Week type books, but the quality really isn't there. I'll wait for the next one to go on sale and see if it improves from this train wreck of a book. If not, I'll be saying goodbye to John Decker.
This entire review has been hidden because of spoilers.
Profile Image for Calvin.
252 reviews6 followers
August 16, 2021
B Movie Plot Hampered By An Idiotic Main Character

This is a fairly enjoyable series, but this one was inexplicably bad. The series isn't perfect. Light on action, decent on mystery, interesting characters, etc. But the main character Decker decided to act like an idiot this book.

Despite having dealt with several unusual and supernatural creatures, when Decker first hears about Grendel he's immediately like "Nope. Not real. Never existed. No way. No." He just completely shuts down to the idea that such a being could exist. I'm not saying he has to immediately belive the myth is real, but at least be open to the idea after dealing with an old woman who turns into a giant werewolf.

Decker also loses all sense of police work when dealing with the apparent survivor of a caving accident. The survivor's story is a flimsy and see through as wet toilet paper. Experienced cop Decker sees no issue with it and doesn't follow up with anything.

Even when it is blatantly obvious the survivor is flirting with him and hiding things, he has no idea until it's too late.

The book could have been so much better if the author hadn't made Decker such a dunce this time around. Hopefully he corrects it in the next novel.
12 reviews
October 13, 2020
I volunteered to review a complimentary copy of this book. John Decker is in Ireland this time on his first outing with his new employers, CUSP. Was Grendel, the mythical beast of Beowulf fame real? CUSP thinks so and a team of archaeologists believe that they have found his grave! Buried beneath the ruins of an ancient monastery lies a cave system that may provide the answers. The ancient village that watches over the caves and the site has its own secrets as well. As the inhabitants begin to go missing the villagers must face the gruesome reality of their acts. Will the truth come out in time to save them?
As always, a new John Decker story is a rollicking good time! My only complaint is that it seemed to take a bit longer for the action/horror to get going. I'll chalk this one up to it being his first assignment on the new job and having to get used to not flying solo. Still a good story and great descriptions of characters and locales. Can't wait for the next one!
Profile Image for Martin Hernandez.
171 reviews3 followers
August 13, 2025
Another fun read in the Decker series.

Throughout the entirety of this book I kept picturing the Beowulf movie from the early 2000s. So much so that I'm going to look it up to try, and watch it again.

Nevertheless, this book is just as fast paced, and fun as the previous 3. Decker get's roped into going to Ireland to help with a dig site connected to a monastery. Things quickly go awry as they're want to do.

Grendel [spoiler? not really...] reminded me of a different book I read wherein the monster was a sasquatch. Feral, and a force of nature; yet intelligent & cunning. Very fun.

Only downside was that I picked up on the "twist" that we get with one of the characters. It wasn't super obvious, but if you know the story of Beowulf & Grendel [roughly lain out in this book] then it is something you can pick up on pretty quickly.

Looking forward, as always to the next book. These are nice little "cupcakes" of storytelling that I can't help but enjoy.
Profile Image for Jennifer.
3 reviews
October 14, 2020
I happened upon this series when looking for something interesting to read. All I can say is they are awesome. I received a complimentary copy of this book. It's set in Ireland so I couldn't resist it. The way Mr. Strong describes people and places is like you're there seeing everything going on. All the character are well written and fully fleshed out. It does start out rather slow, but just keep with it. I read it all in one morning, because I couldn't put it down. I loved the twist, didn't see it coming. I do hope Colum will be in further adventures with John. I can't wait for the next one.
Profile Image for Cat B..
786 reviews7 followers
November 5, 2021
As with all of this authors books, the action starts right away teasing us to go on ... and on ... and on. One more chapter, one more chapter, one more chapter. You can tell yourself this but it will take all your will power to put the book down. The John Decker series are easy reading and very addictive. The descriptions are done in such a way that as you read it is like watching a movie, playing out in your head scene by scene. The gruesome bits are not over done but descriptive enough that you can feel the action in your bones. I so very much enjoy this series and hope they do not come to an end any time soon.
Profile Image for Greg D.
885 reviews22 followers
February 18, 2023
"Grendel's Labyrinth" by Anthony Strong is a chilling and suspenseful thriller that will keep readers on the edge of their seats. Detective John Decker investigates a series of gruesome murders in a small Irish village, uncovering a mystery that is both complex and eerie. Strong's writing style is atmospheric, and he weaves in elements of horror and the supernatural to create a unique and engaging story. The characters are well-developed, and the plot is full of unexpected twists and turns that will keep readers guessing until the very end. Overall, "Grendel's Labyrinth" is a thrilling read that will appeal to fans of crime fiction and horror alike.
Profile Image for Bookworm_0413.
151 reviews5 followers
February 26, 2025
So this has been my favorite book of the series so far. I have not enjoyed reading about Decker even though I love the premise of the books. There is more character development and more enjoyable characters around Decker. Hopefully, they keep getting better.

Spoilers

Towards the end of the book, Rory says that the bullets won't kill Grendel because even the Danes couldn't kill him, thats why they brought him to Ireland. In the beginning, Rory says the historical texts say that they brought Grendels bones after he was killed by Beowulf. Did I miss something in the midst of the book where it was mentioned that Grendel is still alive according to historical text?
This entire review has been hidden because of spoilers.
620 reviews6 followers
December 9, 2025
After John Decker's events in Florida, and his first assignment with CUSP, his new employer, John is sent along with a small team to help out an archeologist who states they have found Grendel's bones. Yes, that Grendel, from the epic poem Beowolf we were all forced to read in High School English class. When they arrive, the two archeologists are missing, and soon Decker and his team have to explore some recently discovered caves to go in search of them. But the town they are in has been keeping secrets. Is it possible Grendel is real, and alive? Until the body count starts rising no one is about to share in information, and the secrets could possibly kill them all.
I am really enjoying this series.
It's part cryptid hunter and adventurer, set in some of the worlds weirdest and dangerous locations.
Definitely worth the read.
837 reviews
June 9, 2021
Another exciting adventure from Anthony Strong. This time we find Decker taking on ancient legend Grendel which is a twist I've never come across. Be prepared for plenty of thrill and chills. This was a fast read with Strong's signature short chapters that keep the action moving. And the last page will leave you eager to start the next book. The shadowy organization for whom Decker now works remains something of an unknown so I'm looking forward to learning more in this area. I am also looking forward to the next book and hoping for a long run for the series.
Profile Image for Mary Brannian.
1,068 reviews19 followers
April 27, 2023
“Not for Tom, I’m afraid.” Father Cleary shook his head. “We’ll hold the funeral in the morning. I’ll be sending the undertaker's first thing. You should say your goodbyes and have him ready by then.” “Just a few days,” Molly pleaded. “That’s all I’m asking.” “I’m sorry. It can’t be done.” Father Cleary took her hand in his. A gentle touch. “We haven’t had a death in the village for almost a year. There isn’t time.”


These words set the tone for a book that will take you on a fantastical journey... Myth, magic and ancient, unknowable evil...
4 reviews
August 19, 2023
Heartstopping!

I discovered this series of books through chance while scrolling through my news feed on Facebook. It was a recommended for you ad. I have always loved the mystery of the supernatural and the legends behind them as well as a good mystery so I decided to take a chance and begin with the first book. I have not regretted it. I have to force myself to put them down. They are fascinating and thrilling and cannot wait to finish them all. This one is definitely filed under one my favorite books tabs and I cannot wait start the next one
6 reviews
October 17, 2020
I volunteered to review a complimentary copy of this book. I could not put it down ! Read the entire thing in 2 days ! In my opinion, this is the best Anthony Strong , he always gives a great read but this is the best yet . Love the references and strong historical links to the Beowulf poem and legend, it all makes perfect but rather scary sense ! Would never have guessed the ending and who was behind it all. A must read.
Profile Image for Cattie Whaley.
299 reviews2 followers
July 27, 2021
Another excellent read

Another John Decker thriller that is hard to put down! Decker finds himself in Ireland on his first assignment with CUSP. Adam Hunt leads the crew of Decker and Colum and an archeological team tasked with finding the remains of Grendel. What they find is not what they are expecting! An edge of your seat ride with a twist I didn't see coming. Highly recommend this book
Profile Image for Stephen.
Author 4 books
July 21, 2024
It's not the best written book. Action is skipped over. Assumptions are made when explanations would have been better. The dialogue in no way feels real. Too many times, we are told rather than shown. There are too many characters.

Yet, I still keep returning to these books. Despite all my misgivings, there is obviously something I enjoy about this series. And the next one is Jack The Ripper, so I'll probably return for that one, too.
Displaying 1 - 30 of 95 reviews

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