Deadly Equation: An AJ Docker and Banshee Thriller

An AJ Docker and Banshee Thriller #4

by Gary Gerlacher

"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.

Genres: Thriller, Mystery, Suspense, Fiction, Adult, Audiobook, Medical Thriller

265 pages, Paperback

Published December 16, 2024

Reviews

[Merry · Rating 4 out of 5]

First let me say I really enjoy this author and I read these books and just suspend disbelief. I rate this one 4.5* There is humor, action, spies and some truly twisted bad guys. Plus, throw in a trained police dog and I am all in. The books are self-contained with no overarching storyline so you can pick up any book and start there. No romance in this one. Enjoyed the historical snippets about DC and I look forward to the next book in the series.

[Anne · Rating 4 out of 5]

This was my fourth book in the AJ Docker and Banshee thriller series, and it was an enjoyable fast paced read.

Doc and Banshee are in Washington, D.C. on a short-term contract in the E.R. where a shady business is trying to seize the contract on E.R. staffing. Besides dealing with those scumbags, Doc gets involved in helping the sister of a dying E.R. patient.

I love how each book introduces new side characters (that helps to keep the stories fresh) and you get a mini tour of notable sights in the host city. Here we have themes of science, particularly mathematics, logic puzzles, and politics/senators/homeland security/Russia spies.

Doc and Banshee have a satisfying amount of page time during this tale and encounter dangerous situations, people on the fringes of society, and a spa-like stay at a highly classified facility.

For those new to the series, you could read them in any order, but if you want the origin story of how Doc and Banshee got together, start at book one. After that, you could pick at personal preference. I’ve liked all four books thus far, however, book three was mediocre. There’s plenty of unique events that made it a worthwhile read, though I didn’t care for Doc’s book three girlfriend. Others may find that book more enjoyable than I did.

Definitely a series that I will continue reading. The sixth book was just released (and is not showing on the GR series link), Phantom Files: An AJ Docker and Banshee Thriller.

[Claire Tauscher Daidone · Rating 4 out of 5]

A traveling ER doctor, an ex police dog and crime. I have thoroughly enjoyed this series .

[Lindsay Pirris · Rating 4 out of 5]

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

[Ed Hornbeck · Rating 5 out of 5]

Excellent series

Main Human character, Doc, is colorful and fun. The dog character, Banshee, is fabulous. The story lines in all the books are well crafted. The characters are well developed and the dialogue feels like you are right there joining in the conversation. Overall this series in my opinion is really worth reading.

[barbara a. woodruff · Rating 5 out of 5]

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.

[Robin Sinex · Rating 5 out of 5]

Another good one!

An easy read, lots of action and suspense! Of course, love, love Banshee. Doc sure finds excitement wherever he goes.

[Kahlie · Rating 4 out of 5]

I really liked this adventure, and this book solidified my wanting to go to Washington DC to explore everything. It was a quick read that really kept me interested and wanting to continue reading. The twist with the senator was one I did not see coming but was a fun twist to everything. There were a couple grammatical errors that kind of bothered me but they're not the biggest deal in the world. I'm sure the next story in Miami will be just as interesting!

[Anirudh Kukreja · Rating 5 out of 5]

A very obvious reveal; but tbh that's the only criticism that I can think of.
Otherwise, the book was fun with a great story; extremely fast pace and Banshee, once again, saves the day and wins hearts.

[Debbie Lanthorn · Rating 5 out of 5]

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.

[Deb Mervold · Rating 4 out of 5]

I am enjoying #4. I am looking forward the the next one

[Bonnie Proctor · Rating 5 out of 5]

Fast paced fun read. I have enjoyed the entire series

[April Winger · Rating 5 out of 5]

Best book so far

Man did I ever love this book,
That dog is delicious! I have never had a dog that would come when I called him so I delight to read about a dog that actually obeys commands. A great read.

[Deedra Dail-whitley · Rating 5 out of 5]

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!!

[KAT A · Rating 1 out of 5]

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.

[Kuita Hall · Rating 4 out of 5]

Politics, international intrigue, genius twins, and murder?

The unlikely combinations felt strained. I longed to read of good guys erasing bad guys to even the scores, but a young genius killed because he is brilliant just seems totally wrong. An equally brilliant sister who can ferret out the murderer doesn’t seem enough for such a vicious event.

Raised on super heroes, I hoped for an all-powerful equalizer to literally destroy the bad guys. Instead, the bad guys loom and plot, and Homeland Security plays an equally dastardly role trying to recover “genius research.” So, a new couple and their amazing dog go against the rest of the world to regain a hidden notebook. The recovery process is more violent than I would prefer (this makes me gag thinking of Gestapo torture!), and an unexpected money and power hungry figure joins the torture party.

My personal muscle cramps were real; I flinch when people swat mosquitoes. So, the tension is on overload, and I worry about the good dog. He’s one in a million.

The book is an easy one day read; time off after this one might be essential.

[Penney · Rating 3 out of 5]

Lacks Depth and Development

This is the fourth book I've read in this series. I am baffled at the lack of character development of the main character and his dog over the four books.

In general, the reader gets to know more about his past or personal preferences. This has not happened. Doc in Book 1 is the same as Book 4. He hasn't changed and we don't know anymore about him.

Also, there are no links between books. Doc never calls people that he developed a strong bond with in previous books.

The main character is an ER Doctor who gets himself into situations that require great strength and a fit body. Yet, the only meals the guy eats are carbs. His meal of choice is grilled cheese and fries with catchup. Even in the most absurd moments, he orders a grilled cheese and fries.

Blanche, his dog is reported to know hundreds of commands yet from book to book, the dog only executes the same simple commands every police dog knows.

I found the storylines in Books 2-4 easy to figure out. For me, books 2-4 have read like AI wrote the books or was used widely to write them.

[T R · Rating 5 out of 5]

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.

[Cathrine · Rating 5 out of 5]

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.

[Vicki Suter · Rating 5 out of 5]

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..

[Jenntleh · Rating 4 out of 5]

I jumped back into my favorite traveling ER doctor, AJ Docker, and his supposedly retired police dog, Banshee. This installment kicks off when a badly wounded scientist is rushed into AJ’s ER after being mugged and shot. With his last breaths he begs AJ to smuggle a flash drive to his sister before the people responsible can get to it.
What should have been a dying man’s simple request quickly spirals into something much bigger. AJ once again puts on his detective vigilante hat and teams up with the scientist’s sister, Mac, to figure out what was on that drive and why someone was willing to kill for it. The investigation pulls them from ordinary city streets into a tangled mess involving Russian spies and government officials, making it clear the scientist’s work was far more dangerous than anyone first realized.
I really enjoy returning to this series. The breaks I take between books keep the story feeling fresh, and slipping back into AJ and Banshee’s adventures is always fun. It’s another solid installment with plenty of action and mystery to keep things moving.

[Daniel Burke · Rating 5 out of 5]

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.

[Travis Tougaw · Rating 5 out of 5]

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.

[Christine · Rating 5 out of 5]

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.

[Timothy Sojka · Rating 5 out of 5]

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.

[Matt Harris · Rating 4 out of 5]

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.

[Cam Torrens · Rating 5 out of 5]

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!

[Joseph Lewis · Rating 5 out of 5]

“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

[Diedre Costic · Rating 5 out of 5]

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.

[Cmoore · Rating 5 out of 5]

I've always liked stories with a Dr. And these are quick and fun...

Here's another credible book in the AJ Docker series. Again Doc and Banshee kinda take the backseat and aren't in the forefront of the mystery. But they're there every step of the way to help solve this murder and find out why... this is Mac's story as she searches to puzzle out the clues her twin brother left her upon his death. And Doc just happened to be the attending physician who received the patient's last message. These books are quick and quite fun reads. Although I believe the author does a disservice to himself and his fiction by not writing a actual blurb for each of his books... I almost didn't download this 'cause I thought it sounded like the last book I read.