Jump to ratings and reviews
Rate this book

An AJ Docker and Banshee Thriller #4

Deadly Equation: An AJ Docker and Banshee Thriller

Rate this book
"The accuracy of medical details and credible bomb threats mixed with genuine characters guarantees an unputdownable read. Buckle in and get ready for a fast-paced ride!" –Ivanka Fear, author of The Dead Lie and Where is My Husband?

A trauma patient's dying request of AJ Docker leads him and his retired police dog, Banshee, to embark on their latest adventures. Partnering with his patient's sister, they embark on a quest to uncover powerful research that could alter the course of humanity. Shadowy enemies pursue them in Washington, D.C., in a race to capitalize on the information, while a new threat reveals itself at Doc's hospital. A greedy corporation is attempting to take over the emergency room, threatening the quality of healthcare nationwide. Doc has to fight a billion-dollar company to save more patients' lives as well as the careers of competent medical professionals. Banshee has his back as he battles on all fronts.

Deadly Equation, book four in the AJ Docker series, delivers nonstop action alongside dramatic scenes from the emergency room. Using his own medical experience, Gerlacher brings readers into the chaotic, sometimes humorous, and sporadically violent world of the emergency room.

265 pages, Paperback

Published December 16, 2024

1402 people are currently reading
900 people want to read

About the author

Gary Gerlacher

17 books373 followers

Ratings & Reviews

What do you think?
Rate this book

Friends & Following

Create a free account to discover what your friends think of this book!

Community Reviews

5 stars
4,902 (67%)
4 stars
1,889 (26%)
3 stars
396 (5%)
2 stars
51 (<1%)
1 star
17 (<1%)
Displaying 1 - 30 of 274 reviews
Profile Image for Lindsay Pirris.
98 reviews
March 26, 2025
Maybe not quite worth 4 stars but the layout of this book was a bit more interesting as there was a scavenger hunt to follow from a dead guy with the typical medical emergencies and police dog work thrown in. Cute series but nothing spectacular.

Ok, bye
5 reviews
December 30, 2024
Another good one!

An easy read, lots of action and suspense! Of course, love, love Banshee. Doc sure finds excitement wherever he goes.
Profile Image for Debbie Lanthorn.
29 reviews2 followers
January 5, 2025
This time set in the nations capital, Gary Gerlacher has combined the emergency room setting and politics in another exciting book. A money hungry corporation is busy trying to take over the emergency room endangering the quality of healthcare to millions. Soon enough Doc and Banshee are in embroiled in the not always honest politics of DC and end up discovering a hidden journal, secret codes and hidden tunnels under the most powerful city in the world.
This entire review has been hidden because of spoilers.
35 reviews
July 23, 2025
A trauma patient's dying request of AJ Docker leads him and his retired police dog, Banshee, to embark on their latest adventures. Partnering with his patient's sister, they embark on a quest to uncover powerful research that could alter the course of humanity. Shadowy enemies pursue them in Washington, D.C., in a race to capitalize on the information, while a new threat reveals itself at Doc's hospital. A greedy corporation is attempting to take over the emergency room, threatening the quality of healthcare nationwide. Doc has to fight a billion-dollar company to save more patients' lives as well as the careers of competent medical professionals. Banshee has his back as he battles on all fronts. Author Gery Gerlacher is an Emergency room pediatrician and the book has medical descriptions occurring as part of the book. Banshee is an amazing well-trained dog and he exhibits his talents in several incidents. The twist at the end of the book was unexpected. Very interesting reading and I could not put the book down until I knew that Banshee was safe and unharmed .HiIghly Recommend reading.
Profile Image for Deedra Dail-whitley.
119 reviews
December 23, 2024
Another Awesome Doc & Banshee book!! Though the ONLY bad thing about this book is that I read it in less than 48 hours!! That’s in between cooking, cleaning & wrapping holiday gifts y’all!! I was taking every possible moment & then some to read this incredible book!! I fell in love with this series from the first book. So I guess before it was a series? Now Mr. Gary Gerlacher is one of my favorite authors! These books are a constant thrill ride, but they don’t come off as unbelievable. I don’t know if I would want AJ Docker to be my best friend, he gets into a lot of complicated messes, but I definitely would want him to be on my side if I was in trouble & Banshee is MY HERO so he’s always welcome at my house!! Keep up the incredible writing Mr. Gerlacher, but if possible please write a just little bit faster!! Again, y’all need to read this book, but I also recommend reading the first 3 books in the series. You won’t be disappointed!!! If I could’ve given this book & each of the three books before it ten stars I would have, In. A. Heartbeat!!! They’re all that good!!
136 reviews
April 26, 2025
Dnf

Read up to page 163 and could no read further. It was a huge struggle to get that far. I know it’s only 200 pages but I could not go any further. I’ve read all the books in this series and rated them 5 stars. This one seems like it was written by a different author. Its plot really didn’t go anywhere. There was absolutely no character development nor any likable characters. The plotline was immensely boring. Unless you want to read all about government boring agencies or inside a corrupt hospital and all the bureaucratic bs involved in that, this book failed for Doc and banshees last adventure. There was no adventure at all. Sad it ended this way.
156 reviews12 followers
August 13, 2024
Gerlacher jumps right in, feeding the reader an action-packed mystery sandwich that doesn’t let up. Page after page through all the twists and turns this is a hard one to put down, costing me hours of sleep. The story seamlessly moves from scene to scene with characters resonating authentic, right down to Banshee, Doc’s god and partner a Belgium Malinois. I loved that dog and all his tricks especially in the ER helping patients relax, and if anyone has ever seen one in action working with the police they’ll appreciate the impeccability of character development in this novel, yes, right down to the dog. The added detail work in the various scenes brings the story to life. Gerlacher is a good storyteller, writing effortlessly without lags or slows or overdone descriptions, and with a touch of humor, interspersed at the right moments, lightening the story just enough to not distract from the dangerous theme. After I finish, down to the satisfying ending, I’m ready for more from the talented Gerlacher. Highly recommend.
Profile Image for Cathrine.
1,154 reviews8 followers
March 30, 2025
Doc and Banshee are in the DC area now

They unsuccessfully try to save the life of a DARPA researcher, Mark Lawton, who may have found the key to curing every disease imaginable by altering DNA, but this could also become the ultimate weapon. Using his dying breath Mark asks Doc to give whatever is his pocket to his twin-sister Mackenzie, call me Mac, Lawton, who is the Chief of Staff for Senator Whitehurst.

Turns out the Department of Homeland Security, the Russians, and Senator Whitehurst want whatever research is on the thumb drive that Doc gave to Mac, but the information is unobtainable by anyone but her because Mark made getting the password a scavenger hunt that on,y Mac, with a little help from Doc and Banshee can solve.

As a side plot a large investment group is trying to take over the staffing and running of the emergency room in which Doc works. He,the Head of the Emergency Department, Dr. Pastone, and The BT (the hacker from previous books) do their best to turn the tables in this group.
1 review1 follower
December 6, 2025
Worth reading again and again

Dr. Gerlacher, this my second pass through your AJ Docker and Bannshee thrillers. I imagine it won’t be my last. Every single book is masterfully well-written (I bet your wife had a lot to do with that, and I appreciate that you give her the credit due her). I enjoyed all of the books on my second reading as much as I did the first (less than a year ago), because they are nuanced, multi-layered and wrestle with authentic challenges in different institutional settings. Each book immediately engaged me, and gave me the opportunity learn about these different settings, through clearly written, research-based and personal experience.

I am a voracious reader, but this is my very first book review. I’m posting it because I expect you read your reviews, and I wanted to let you know how grateful I am for your hard work. These are tough times, both personally and more generally in the world, and I appreciate the respite of stepping out of it and spending time in the places you have described and the people you have created..
Profile Image for Daniel Burke.
Author 3 books46 followers
August 14, 2024
I was fortunate enough to receive an advanced copy of Gary Gerlacher's latest book and wow! You never know what adventure will come through the emergency room doors and into Doc and Banshee’s lives. This time, the pair are in Washington D.C. when a gunshot victim is brought in carrying a dangerous national secret that will land them in the crosshairs of international spies and duplicitous politicians. Full of AJ’s wry humor and decency, Banshee’s heroic deeds, and the warmth of their relationship, the story is exciting without being overly violent or dark. The plot contains some interesting and familiar Jurassic Park-like elements that I found enjoyable. I’ve read all four of the AJ Docker books, and this is my favorite. It has all the elements of a great edge-of-your-seat spy thriller, and like the other installments, it stands on its own. You don’t have to read books 1-3 to enjoy Deadly Equation, but you’ll want to.
Profile Image for Travis Tougaw.
Author 4 books40 followers
August 23, 2024
The latest installment of the A.J. Docker/Banshee series, sees Doc and his trusty canine companion in Washington, D.C. When a mysterious patient shows up at the ER with a gunshot wound, his dying wish is for Doc to deliver a flash drive to his sister. Doc follows through and becomes embroiled in a scavenger hunt to find clues that will lead Doc and the patient’s sister to potentially world-changing research. They aren’t the only ones interested in the research, though, and Doc soon finds himself in a battle with enemies both foreign and domestic. Fortunately, he has Banshee by his side.

Written with Gerlacher’s trademark blend of action, wit, and memorable characters, Deadly Equation is a fast-paced game of cat and mouse (and dog) you don’t want to miss. Whether you’re a fan of the series (like me) or you’re just meeting Doc and Banshee for the first time, Deadly Equation will keep you flipping pages and wondering who you can trust all the way to the gripping conclusion.
Profile Image for Christine.
302 reviews6 followers
July 6, 2025
Deadly Equation
Gary Gerlacher
July 2-5 2025
5☆s
Book 4 of Doc & Banchee series
Each book that I have read in this series just keeps getting better & better. Of course I probably said the same about the first book in the series. The characters are well developed, even the minor ones. The book moves along with a well developed plot. Everything has been well developed & it does't slow down until its over. I really liked this story line. There were several plots going on at the same time & yet they all worked together. I had been thinking about watching the Nicholas Cage movie about secrets, treason, and the theft of the famous document from Philadelphia since it was the 4th of July and then Gary made a reference to the movie. It was an excellent read & moved through the storylines at a nice pace. I gave it 5 ☆s for creativity, excellent characters. storyline, and plot. I'm looking forward to more books in the series of Doc & Banshee.
Profile Image for Timothy Sojka.
Author 5 books57 followers
September 27, 2024
Having grown up main lining Robin Cook, I found myself drawn to Dr. Gary Gerlacher’s newest novel. Gerlacher who honed real world medical skills in some of the nation’s most demanding Emergency Rooms (shout out to Ben Taub for my Houston based friends) shows off his writing chops in his upcoming thriller Deadly Equation. Yes, for those of us who binged way too much Grey’s Anatomy, ER, and House, Gerlacher offers us enough medical trauma to quench that thirst. However, make no mistake, Gerlacher’s medical background, shared with his protagonist AJ Docker, simply serves as the appetizer before the author’s main-course-thriller stocked with great characters. Dog lover’s will be entranced by the best trained K9 in fiction, Banshee. A lot to love in the novel.

Timothy Gene Sojka, author of #1 Amazon Thrillers Payback Jack, Politikill, and the upcoming Claws.
26 reviews
January 28, 2025
This four book series by Gary Gerlacher is quite enjoyable! My favorite of the three is Sin City treachery but this fourth book is fun and somewhat complicated given that math is involved. I think that the main characters AJ (Doc) Docker and Banshee (former police dog) are well defined and great to follow from city to city. To understand the origin of their friendship, the reader would have to read the first book in the series. There are some characters whom I would love to see back again and was pleased that Lana from Sin City made a brief return to this book. I was starting to think that Doc suffered from a mild attachment disorder. Each book can be easily read in two days or less. The intermixing of medical cases in the ER with the overall mysteries and thrillers are wonderful. Doc is moving on to another city and I expect to read a fifth installment soon.
Profile Image for Cam Torrens.
Author 5 books116 followers
August 14, 2024
Gary Gerlacher disrupts my sleep cycle again, delivering another AJ Docker & Banshee Thriller/Mystery I can't stop reading!

This one was brilliant, weaving together two storylines: the first, a tactical challenge with strategic implications--unidentified enemies attempting to use groundbreaking research to change the world; and the second, a strategic public/private policy challenge in medical administration with a tactical impact at the Washington DC hospital where Doc works. Gerlacher seamlessly blends action into both quests, with Doc and Banshee (as usual) racing against time to save everyone.

This fourth installment in the AJ Docker series offers nonstop action, intense medical trauma scenes, and a gripping fight against corporate greed. You gotta read it!
Profile Image for Joseph Lewis.
Author 11 books101 followers
November 18, 2024
“A dying man’s gasping last wish to an ER doctor with the words, “Trust no one.” Lethal foreign spies, listening devices, and secret tunnels. Doc, Max, and Banshee are followed by governmental agencies as they hunt for clues to find the secret research that could change the world. All of this and more make up the tight, multi-layered thriller, Deadly Equation by Gary Gerlacher. A fascinating must-read if you are a thriller-mystery enthusiast. It had me hooked from the first page to the last, and it is one of those books that keep you guessing as it leads you to believe one thing through subtle clues and hints, only to reveal a different path. I recommend this terrific 5 Star Read wholeheartedly and enthusiastically.” Joseph Lewis, Reviewer and Author of Fan Mail and Black Ye’ii
13 reviews
May 31, 2025
Another Great Read

Suspense, murder, mathematics, science, biology, research, politics and an awesome dog all in one novel. Doc finds himself in an international and national situation that is based on scientific research. A dying patient asks Doc to deliver an item to his sister. This leads to espionage , kidnapping and many secrets.
The read is fast paced as the characters must search for clues while being followed by government agencies and foreign nationals. Of course Doc's beloved companion Banshee is at his side. In addition to all this the hospital is dealing with corporate greed. Unfortunately this is based on fact.
I highly recommend this book which Book #4 of a series.
Profile Image for Niamh McAnally.
Author 5 books50 followers
August 13, 2024
Another engaging story in the AJ Docker and Banshee series from Gary Gerlacher. It’s like catching up with an old friend who always has new escapades to share. Each book finds the duo in a different city. In this one Gerlacher superbly weaves a fast-paced plot with a wonderful tour of Washington D.C.’s historic monuments. The scene of the changing of the guard by the tomb of the unknown soldier is particularly moving. But AJ and his new friend Mac can’t dally for long as Russian operatives and Homeland security agents are close behind. Fans of this series will be kept busy trying to solve the clues of the quest facing AJ and Mac, and meeting some new unusual characters. Highly recommend.
Profile Image for Krista.
229 reviews8 followers
March 9, 2025
all are good—this one is the very best in the series

These books are entertaining candy to me. I consume them quickly and they take me away from my stressful life to a whole other world of pressure I will never encounter, which is a relief and an escape. This one is remarkable. Though not entirely perfect (a few random typos, for instance) it is thrilling, interesting, and even made me cry a couple of times. I’ll take this story with any minor flaws over crap fiction that makes me feel nothing, every single day. Ultimately redeeming and hopeful, it’s worth any reader’s time, and solidified my desperate desire for a female U.S. President…and a Banshee!!!
20 reviews
March 12, 2025
Another great book by Gary Gerlacher. Was a little slow in the process of finding the various clues but certainly picked up in the last third of the book. Nice twist at the end with the senator getting involved. Makes you wonder about what goes on in real iife with regards to our congressmen. Always thought there might be a romantic connection between Doc and Mac but did not happen. Interesting the exposure of the scam regarding corporations taking over Emergency Rooms. Seems this is not far from the truth as corporations are buying dermatology practices as well, in the past they were hot on buying surgery centers. Looking forward to the next Doc and Banshee book.
3 reviews
June 6, 2025
A Delightful Discovery

Well, Dr. Gerlacher, I was browsing around and happened upon what I thought could be an interesting new read. I chose the first book of the AJ Docker and Banshee series. Fell right in love with Banshee and Doc. Finished the first book Monday, read the second book Tuesday, the third book Wednesday and just finished the fourth book here Thursday evening. I'll be watching for the fifth book! I'm ready! I enjoy all your characters and your plots, the medical background and your accuracies when used. Heck! I just really enjoyed your books! Kudos to the great team you've assembled. Wishing you continued success!

Judy Micelle
2 reviews
June 13, 2025
Washington good and bad

Washington is full of surprises. From politics to foreign intrigued , there is one adventure after another. I enjoyed all the descriptions of historic places. I do get a bit tired of the Russians being behind every big secret.
I am sure the history of Arlington National cemetery was researched, but not accurate. The land used for the cemetery was confiscated from Robert E Lee as punishment for leading the troops from the South. Lee was a descendent of George Washington.
Also, I didn't care for the torture of A J. The talents of Banshee are amazing. I do worry about his diet.
M Harper
Profile Image for Delores.
101 reviews1 follower
July 13, 2025
Love this series!

This author is new to me. I am now on the fourth book in the series and I can truly say I have thoroughly enjoyed them. I enjoy the medical aspect of these books as I am a retired critical care, nurse of 20+ years. I enjoy the mystery and action of these books as it keeps you engrossed and entertained. I appreciate the humor and insight into the different characters, particularly those in the ER as I am so familiar with those kind of relationships and actions
I can’t wait to read the next one. I have truly enjoyed this author’s work and his style of writing. Great job and great stories.
Profile Image for Dana Goosen.
140 reviews2 followers
August 7, 2025
2 - 1 -> 1*

What a stupid move add someone nicknamed Squirrel into every book 🤮 it’s not an Easter egg, it’s pretty irritating. Minus a star for this.

Honestly, this book is the worst so far in the series. I’m so glad I’m finally done with them. I bought all four as a bundle. The first one was really enjoyable and each next one was worse and worse. This one has the most boring pace, tons of cliches and Doc is not the same character he used to be in Book 1. He’s mostly eating or walking around like an NPC. Episodes at the hospital are just fillers.

Finally it’s over. Off to read something less irritating.
Profile Image for Jackie Martello.
269 reviews2 followers
October 22, 2025
I read all the previous books in this series and enjoyed them, but this one was a little underwhelming. The book had its moments, but I thought the story was a bit disjointed and the ending was completely anticlimactic. The antagonists were not satisfactorily dealt with, and even Banshee as a character was less interesting. Unfortunately the series is slowly evolving into a woke mess complete with tough boss ladies everywhere and a weak main character. In fact all the characters were somewhat lifeless and colorless. The terrific humor from the first book is completely gone. I hope the next one is better…
76 reviews2 followers
December 12, 2025
Disgraceful Medical Practices?

Great characters in this book, and in the whole series! I enjoy the different locations that Doc and his awesome dog spend time in. The medical issues in this book are probably much truer than we realize. Seems like everywhere you look, the administrators are the ones making the money; and in the medical field you have insurance people who are many states away from you deciding whether you need the procedure or hospitalization ordered by the doctor who examined you or not. This is ridiculous, and I enjoyed seeing this big corporation taken down. Looking forward to seeing what happens next in Florida!
19 reviews
October 19, 2024
Deadly Equation by Gary Gerlacher is both an intelligent and fast-paced read for anyone interested in both espionage and medicine. His take on modern usage of ancient DNA is an original take on Crichton's ideas, and is an exciting intersection between medicine and criminal scheming. The intricacies of the puzzle-solving thrust on his characters kept me interested until the end. Both an educational and entertaining thriller.
-Scott Eveloff MD, author of The Golem's Holocaust and Do Not Resuscitate-
Profile Image for Janet Graham.
2,506 reviews11 followers
December 20, 2024
Un-Put-Downable DC Thriller
This book is the fourth book in a series of great thrillers. Books three and four should be read in order due to some overlapping content. Personally, I think the entire series should be read in order for the reader to fully understand the back story. In this episode, our ER Doctor is working in DC and is staying very busy. He and his 'retired' police dog are pulled into unexpected intrigue with international complications. I didn't want to put this one down, even to sleep. I can't wait for the next episode to be released.
33 reviews
January 1, 2025
ANOTHER DOC & BANSHEE HOMERUN

I've read all of this series and love these books. Whenever I pick up a Gary Gerlacher book, my time is unavailable until I finish the book. I literally cannot put it down or sleep until I finish it. This story has all of the exciting ER drama, with Russians, Homeland Security and corrupt politicians chasing after the hero, heroine, and dog stars of the book. It us incredibly well written and edited. I only found one small error. Highly recommend this author, this book and the entire series.
Displaying 1 - 30 of 274 reviews

Can't find what you're looking for?

Get help and learn more about the design.