Phantom Files: An AJ Docker and Banshee Thriller

by Gary Gerlacher

" Phantom Files is a bestselling medical thriller that may cause readers to experience rapid breathing, heart-pounding, spine-tingling, page-turning excitement." -Gail Ward Olmsted, author of the Miranda Quinn Legal Twist series

A brutal murder of a well-known and respected senior physician at Tempe General shocks the community. But it's just the beginning-a violent avenger stalks the hospital's corridors and more people may be on his kill list.

After AJ Docker fails to resuscitate the first victim, he is determined to prevent further violence. With his friend Dirk at his side and Banshee guarding his back, Doc hunts for the killer. His inquiries uncover the hospital's dark, sordid past and lead him to seek files rumored to contain information that might identify the killer. No one knows whether the files actually exist, and it's unclear who is helping Doc and who might be helping the killer.

Phantom Files once again showcases Gerlacher's medical knowledge skillfully integrated with a complex plot full of twists and turns. The pace is fast, the action intense, and the characters unforgettable-as readers have come to expect from this bestselling series.

Genres: Thriller

282 pages, Kindle Edition

Published March 5, 2026

Reviews

[Anirudh Kukreja · Rating 5 out of 5]

The final part (as of now) in the AJ Docker and Banshee series was definitely one of the better ones. Don't have much to say, other than the fact that I really enjoyed this book; it went back to the old formula of the series being a whodunnit as opposed to the whole terrorism/political genre that a few books fell into.
Will definitely miss Banshee - you're not just a good boy, but the best boy!

[BAMF_Book_Nerd · Rating 5 out of 5]

Phantom Files by Gary Gerlacher is book six in the AJ Docker and Banshee Thriller series. My goodness, every time I think this author can't top his previous book, I'm quickly proven wrong. I love how this read includes a few differences from the previous books in the series, such as how the murders are carried out and a new way that Banshee locates Doc.

[Hannah Murphy · Rating 3 out of 5]

3.5⭐️

[Paulette Mahurin · Rating 5 out of 5]

Doc and Banshee are in a busy ER in Phoenix when a slew of doctors are brutally murdered setting Doc onto the investigation. For him it’s personal as he responded to the code blue calls ending in his giving the time of death. Having to deal with the stress from the unhelpful arrogant hospital Administrator and Head of HR was eased by a few friends: Dirk, the food loving ER guard, Sue the ER head nurse, and his partner Banshee. The interplay of characters is extremely well done as the scenes move from a horrific MRI scene, to a lethal chair, and on, as suspects start to reveal themselves but one clue is undone by another revelation and it’s hard to know who done it until the last few pages. Even then the mystery continues as Doc’s life is in danger. The intensity of the danger screams from the pages with six deaths in the wake of destruction. I loved so much about this gripping fast read, how Dirk ate for three and how doc kicked him under the table when he said something inappropriate bringing levity into the horrors befalling doctors. The ER and medical scenes were spot on and the manner in the way the deaths constructed ingenuous. But what I loved the most was Docs relationship with Banshee and how Banshee scoped out friend from enemy in a portrayal that a dog lover as myself resonated with. There’s a lot of heart in this story, in the caring way Gerlacher dealt with hospital patients and in the final analysis when he could have he did no harm. I’ve read his others book but there was something very addictive about this one and I can’t stop thinking about it, how much I looked forward to my daily read and when I came close to the last page I slowed the read to make it last feeling a little disappointed it was almost over until I saw DOC’S GOING TO SAN DIEGO! Thank you, Gary Gerlacher for giving this reader several happy days of enjoying your storytelling.

[Hannah McNamara · Rating 5 out of 5]

Phantom Files sucked me in from the first sentence, completely immersing me in Dr. AJ Docker and K9 Banshee's world of brave heroism and medical nightmares. Set in a hospital in Phoenix, Arizona, this thriller is packed with action and full of mysteries. A serial killer lurks in the shadows at Tempe Memorial Hospital, killing senior doctors in brutal and strange ways, but being elusive enough to not get caught. Doc can't help his curiosity surrounding the deaths, leading to him, Banshee, and ER guard, Dirk, doing their own detective work to figure out who's betraying the hospital's doctors. Right when readers think they've figured out who the killer is, Gerlacher comes in with his creative storytelling and attention to detail, ensuring you'll be guessing up until the very end! Gerlacher has a knack for forming relatable characters and impressive plots, and I thoroughly enjoyed reading his work. -Hannah McNamara, author of Gut Instinct.

[Cam Torrens · Rating 5 out of 5]

A lightning-paced medical thriller blending suspense, mystery, and action. Dr. AJ Docker and his retired K9 partner, Banshee, rotate through emergency rooms across the US. While in Tempe, Arizona, the duo find themselves entangled in a series of hospital murders where they are always the first on the scene. Despite Doc's efforts to stay out of the police investigation, his instincts and unconventional methods inevitably result in him uncovering chilling secrets hidden within the hospital walls. As the danger closes in, Gerlacher ups the tension, making this another unputdownable read for fans of crime fiction with a medical twist.

[Bob Rothman · Rating 5 out of 5]

With his sixth medical mystery thriller, Gary Gerlacher ratchets up his already superb game, grabbing readers on page one and daring them to put the book down. Few will be able to do so. An intricate plot features Gerlacher’s two omnipresent characters, itinerant emergency room doctor AJ Docker, and Banshee, his German Shepherd with keen instincts and a personality all his own. The story is set in a Tempe, Arizona, hospital where too many people are dying. The problem is it’s not just the patients who are dying! Hippocrates is surely turning over in his tomb while waiting for Doc and Banshee to solve Gerlacher’s latest, and best, medical murder mystery.

[Julia Shraybman · Rating 5 out of 5]

The Phantom Files delivers a deeply satisfying mix of medical realism, suspense, and psychological tension. Gary Gerlacher creates a vivid hospital world where every detail—from emergency room chaos to inter-department politics—feels authentic. The murders are unsettling and cleverly constructed, and the “Avenging Angel” plotline kept me guessing the entire way through. Dr. AJ Docker and his dog, Banshee, bring heart and humanity to the story, grounding the intensity with warmth and humor.

This is my fourth book by Gary Gerlacher, and I continue to be impressed by how immersive, sharp, and utterly engaging his storytelling is. A standout thriller from start to finish

[Lena · Rating 5 out of 5]

Doc and Banshee have more lives than a cat, as once again, they become embroiled in danger as they help solve a crime. When one of the hospital's own doctors is the patient killed during an MRI, Doc is on duty for the gruesome scene. With the clock ticking, he searches for a killer within the hospital, only to uncover long-term blackmail, narcotics theft, and a string of additional murders. With fast-paced action, compelling characters, and the best canine sidekick around, Phantom Files is a recommended read for thriller and action lovers.
I received an ARC from the author and have left an honest review.

[Anne Palmer · Rating 5 out of 5]

Unputdownable

Another excellent Gerlacher story where murder is always involved. I have read the entire series and he makes each one unique. I live in Tucson and it crossed my mind to look up the corrupt hospital this story was centered on, but correctly decided he wouldn't use a real hospital there unless he wanted an army of nurses and doctors hunting him down! I appreciate the fact that he leads us to the real killer slowly over the course of the book, and doesn't suddenly reveal him in the last chapter with conclusions you never could have seen coming. Other mystery authors do that and it's frustrating. Great job, Gary. Keep 'em coming!

[Kim · Rating 5 out of 5]

Gary Gerlacher’s latest book, Phantom Files, is everything I’ve come to love about this series. This non-stop medical thriller plunges ER physician Doc Docker and his loveable, retired police dog, Banshee, into a chilling investigation at a Phoenix hospital where a killer known as the “Avenging Angel” is targeting doctors. The plot takes surprising twists and turns as Docker uses his medical expertise to hunt for the killer’s identity while his trusty dog protects him from the killer’s attempts to stop him. I highly recommend this action-packed thriller for fans of medical crime fiction.

[Lucille Guarino · Rating 5 out of 5]

A killer who calls himself the Avenging Angel besieges a Phoenix hospital. With unwavering tenacity and his sidekick Banshee, Doc once again sets out to assist—or rather, to expedite—in the investigation of the murders of high-ranking doctors. The Phantom Files deals with a new terror. A sophisticated killer. Brilliantly scary and more sinister than any Doc has encountered before. I read this book in two days, completely immersed and stunned. Book 6 of the AJ Docker medical thriller series lives up to its earlier installments and might just be my new favorite!

[Addison Brae · Rating 5 out of 5]

In Phantom Files, Gary Gerlacher delivers everything thriller readers want - greed, murder, and good guys (and dogs) fighting for their lives. The latest AJ Docker "Doc" adventure is packed with:
- One badass doctor with a conscience and strong will to stop anyone who means harm
- One lovable, loyal killer super dog
- High body count
- Countless tense moments that will make you second-guess your next hospital stay 

With a killer who's described like this, "Killing was simply a means to an end, like brushing his teeth." readers will stand behind any form of Doc's justice. 

[Cindy · Rating 5 out of 5]

Love this series!

Not for the squeamish, but the author definitely understands the medical profession. Several deaths, a list of people with some names crossed off, and some files taken lead Doc and Banshee on the trail of a killer. I look forward to Doc and Banshee in San Diego in the next book. I recommend that you at least read the first book in the series to understand how Doc got Banshee. No cliffhangers in the series.

[Sandra J Cady · Rating 5 out of 5]

Phantom Files: An AJ Docker and Banshee Thriller. AJ Docker and Banshee take the reader on another fast-moving thrill ride. Gerlacher keeps the suspense high as the murderer eludes the police and Docker and Banshee get involved. Warning: The first murder scene is an unforgettable humdinger and sets the pace for the rest of the novel. Altogether, a thoroughly enjoyable read.

[J · Rating 5 out of 5]

Another Unique Read

Gerlacher does the most unique story lines. Books are engaging and worthwhile. Interestingly, most of his books are only in our state correctional library and can’t be loaned to other libraries. So you have to buy them, but they are great entertainment and worth it.

[Julie Janssen · Rating 5 out of 5]

Worth the wait!

It was worth the wait for this latest installment in the Doc and Banshee series! Lots of realistic and crazy Emergency Department drama. Love the pace of the writing and lack of spelling/grammatical errors. Only found one! Looking forward to the next book! Ret. PACU RN

[Kirk Hodges · Rating 5 out of 5]

Another great read

Was very pleased to see the author had posted another Doc and Banshee adventure. Wasn’t disappointed and thoroughly enjoyed this one. Now on to San Diego and the next adventure. To anyone thinking about this author and his works, immediately get involved in all the series about Doc and Banshee. You will be entertained and rewarded.

[chris daddario · Rating 5 out of 5]

another great story

Love these books. They combine everything a good thriller needs, mixed with some really comedic episodes. It’s always fun trying to figure out the “bad guy” in his books, and more times than none I have been surprised…yet it was believable and made sense. Looking forward to his next San Diego adventure….hope it’s soon!

[Janet Hall · Rating 5 out of 5]

Gerlacher hit it out of the park again

I fully admit to being obsessed with this series. An ER Doc who Is a wannabe cop and I'm so totally in love with Banshee. His canine side kick. Together they make an awesome team. And do they ever kick some a$$!!!!! I have followed them through 6 cities now and can not wait to see what happens in San Diego!!!

[Karen Lowe · Rating 5 out of 5]

Page turner

Another exciting mystery for Doc and Banshee kept me reading until the end. Whew! Horrific deaths, deceit, some questionable sleuthing, and personal risks culminated in catching the bad guy. Very satisfying and entertaining!

[Julia Lawrence · Rating 5 out of 5]

love it

Go Banshee. Woof woof woof. You are wonderful. Gggggggggggggggggggggggggggggggggggggggggg Banshee banshee banshee banshee ba nshee. Banshee banshee banshee banshee banshee

[Mary · Rating 5 out of 5]

Excellent

Nothing new for Doc and Banshee including investigating murder. The plot was filled with red herrings and would-be accomplices, and I had no idea who the killer was until they were revealed in the book. This book deserves ten stars.

[Shellyann Paape · Rating 5 out of 5]

Murder in the Hospital

Ever wonder what happens when doctors need their secrets to be kept? Wondering whether or not phantom files exist in a hospital near you? I personally am.

Banshee, Doc & Derek make a great team.

I’m ready for the next adventure in San Diego

[Shana Pare · Rating 5 out of 5]

I do love AJ and Banshee!

Yep, Banshee strikes again ... And again ... and again, saving the Doc from deadly harm! Along the way, he also performs tricks to entertain tired nurses and frightened patients. Banshee is such a good boy!

[Meghan · Rating 5 out of 5]

fast paced great read

Love the bond between Doc and Banshee. Fun books that don’t make you think to hard and you can just enjoy the story, unfolds naturally and being a dog lover makes these a quick favorite.

[Caleshe Voges · Rating 5 out of 5]

Doc and Banshee do it again

Doc and Banshee on another thrilling adventure with murder, mystery and more than half be attempt on their life. Gary is a great writer can’t wait to see where Doc and Banshee’s in San Diego lead.

[Joan Brigham · Rating 5 out of 5]

Always A Pleasure to Read

Gary Gerlacher has a winner in the AJ Rocker series! Banshee is a character dog that actually makes me want a dog! AJ is a great character that engages the reader from the start of the series. Definitely a good read!

[Linda Peel · Rating 5 out of 5]

AJ Docker and Banshee never disappoint

I discovered Gary Gerlacher on Kindle Unlimited and he has become one of my favorite authors. If you have not read this series you are in for a treat

[Laura Coats · Rating 5 out of 5]

I have read every book in this series and have enjoyed reading about Dr. Docker and Banshee. The books are easy to read and make you want to keep reading to find out who is "the bad guy." Looking forward to the next one!