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Forensic Geology #5

River Run: Mystery in the Wild: The Forensic Geology Series, Book 5

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—USA TODAY BESTSELLER

—THERE ARE PLENTY OF WAYS TO DIE in the Grand Canyon.

Forensic geologists Cassie Oldfield and Walter Shaws investigate one trouble on the canyon's Colorado River. Stranded raft. Life vests unused. Rafters missing.

The only clue to the fate of the rafters is a bag of pebbles caught in the bowline. Following that clue, the geologists uncover a hellish scheme. Not only are the rafters in peril, but the river itself is under attack.

The race to stop it takes Cassie and Walter deep into the canyon, and onto the mighty river, putting their own survival at stake.

—All books in the series are standalone novels and can be enjoyed in any order.

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Published August 12, 2024

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Toni Dwiggins

14 books74 followers

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5 stars
245 (42%)
4 stars
180 (31%)
3 stars
107 (18%)
2 stars
28 (4%)
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13 (2%)
Displaying 1 - 30 of 48 reviews
47 reviews
April 17, 2019
Las Vegas is a fascinating city. Nearby is the Colorado River, plugged by Hoover Dam to create Lake Mead with its deep bathtub ring marking the southwest's many-year drought. A place to jump off to all the spectacular points in the Great Circle of national parks.

When you live here amidst the palms you understand that the finer life often bumps up against water fears and the odd pointy desert critter, nestling in the brush. Sort of like the ear in the lawn, seen in David Lynch's Blue Velvet.

April is the best time of year, too. What's left of the spring chill hangs north of the Mojave but the scorpion's breath of summer is still a month away. Cactus blooms burst everywhere and the ocotilla extrudes its scarlet clusters. And if you live on the eastern side of town, near Tropicana, you'll hear the five-times-daily rumble of flights of helicopters hauling tourists to the Grand Canyon.

It turns out that one of those flights we heard last April wasn't the commercial tourist run after all. It was geologists Walter Shaws and Cassie Oldfield at the end of their flight from the Dolores down the Colorado to Hoover Dam and Las Vegas. These two are the main characters in Toni Dwiggins' Forensic Geology series and the stars of her newest volume, River Run.

Ever since I read Volcano Watch, the third book in the series, I've compared nearly everything I've read to it. It's the pre-eminent five-star thriller, bar none. But now there's competition.

Cassie and Walter are comfortably engaged in a Grand Canyon geological documentary when things go badly awry. An empty white-water pontoon boat has washed up in mid-canyon. It contains a pristine baggie of rock samples. Shaws and Oldfield are brought in to pinpoint the source of those chips in order to try to find any survivors.

It turns out that the rafting party may or may not be a fishing expedition hosted by a close but dead friend of Walter's. Several years dead, in fact. Leading us into ever-stranger eddies and curls as we work our way through the Grand Canyon and its great river.

The writing is first class. If there is any disappointment at all, it's that the book swept by so quickly. Dwiggins' knowledge of the field and the way it interacts with life from Colorado to California is incredible. And her ability to guide us easily through the rapids of schist and shark's teeth and halite inclusions is simply uncanny. Combine that with a real sense of character and you have a top-notch thriller.

You could not ask for a better ride. Buckle up your river gear. You're going to need it.
504 reviews5 followers
September 11, 2024
A marvelously realistic mystery set in the Grand Canyon
Audiobook version: 5 stars overall, 5 stars story, 5 stars narration

A boat-full of whitewater rafters has disappeared due to either accident or foul play, and they need to be found before they die in the harsh conditions of the Grand Canyon. Tension runs high in this thought-provoking and fascinating mystery.

Fans of national parks would love it because the story has authentic geography and features of the Grand Canyon. I loved the thrilling whitewater rafting as well. The main characters Cassie and Walter are really likeable people and talented investigators. Their expertise is forensic geology, but they also follow through on clues and interview witnesses as they work with an FBI agent and a park ranger. I highly recommend this book to anyone who likes smart mysteries. It is possible to read the series out of order, but I find it more rewarding to read in order.

The narrator Nellie Scott did an excellent job. Her alto voice is very pleasant and really brought the story to life. All of her character voices were very distinctive and sounded right for each character. Her pacing was perfect, and her comic timing and emoting were just right. Partly because of her narration I was glued to this audiobook.

I requested and received a free audio copy via the publisher, and I voluntarily wrote this honest review. #TheFlockVIPReviewTeam #FiresideAudio
Profile Image for Brenda Whiteside.
Author 26 books310 followers
February 25, 2020
This novel is a tale woven around forensic geologists and the Grand Canyon. I didn’t know there was such a thing as forensic geologists. Rafters are missing and foul play is suspected. Cassie and Walter use pebbles and rocks to follow the clues. If you like really detailed information about rock formations and river flow within the Grand Canyon, you’ll find this story interesting. The geology details overwhelmed the story in my point of view. At times, I didn’t understand why the geologists were even involved. There is a subplot about the river being under attack that seemed forced. But if you enjoy geology with your suspense, you’ll enjoy the book.
26 reviews
September 27, 2020
The story line is so choppy, it's hard to follow.

I read a lot of suspense books. This book had such potential to be a great story, but I found it difficult to connect one chapter to the next. So many times the author did such a large jump in the story line that I thought I must have missed several pages. The characters were not well developed which prevented developing a connection with them. The concept of forensic geologists is very interesting. I hope the author is able to bring further stories to life.
335 reviews
April 10, 2020
Caught crook in a lie - finally

Complicated crime, elaborate investigation, poorly plotted. Sole survivor of Grand Canyon boating accident has traumatic amnesia and a story inconsistent with other evidence. Investigators spend last third of book trying to catch survivor in a lie. Plot moves slowly in attempt to tie up all the loose ends.
Profile Image for Mike Giess.
111 reviews
September 20, 2021
Toni Dwiggins’ forensic geology series of books usually give me a thrill ride, but this 5th book in the series just doesn’t do it. I found the plot line needlessly convoluted and hard to follow. The Grand Canyon setting was a superb setting for a wonderful tale for her geologist protagonists but Ms. Dwiggins botched this one by making it a tedious read.
Profile Image for Al.
1,335 reviews50 followers
February 29, 2020
This is the fifth book of this series and the second that I’ve read. By virtue of the basics of the series you’re going to have some forensic geology involved. That is, after all, the name of the series. But you’re also going to have some unique outdoor settings throughout these books. In this case you’ll get a chance to explore, along with Cassie and Walter, the area of the Grand Canyon with a brief foray into the red rock area of Southern Utah as a bonus. If you’ve visited the Grand Canyon, you’ll be able to imagine what Cassie and Walter are seeing. If you’ve ever taken a ride on a raft down a river, your knuckles will turn white as Walter and Cassie run rapids on the Colorado River in the Grand Canyon. It’s a fun time.

Oh yeah. I almost forgot. There’s also the mystery at the heart of the story. What happened to the rafters who have gone missing? Figuring that out will keep you on the edge of your seat too. Just be sure to hold on tight and whatever you do, don’t take off your life vest.

**Originally written for "Books and Pals" book blog. May have received a free review copy. **
Profile Image for Linda Thomas.
842 reviews9 followers
September 21, 2020
Cassie and Walter are forensic Geologists who have taken a job in the Grand Canyon as a break from there job.

Cassie and Walter have taken a dream job for Geologists, a documentary on the Grand Canyon. Since they are both forensic geologists this is supposed to be a working vacation for them. But they aren’t on the job one day when they are borrowed by the Search and Rescue to help find where in th canyon raft had been tied up and the crew los? Then the FBI is involved and more people are missing and killed.
This is an extremely well written book. Having lived in the areas they talk about it captured my attention and didn’t let me go. The people are believable and you get caught up in the story from the first page to the last. Fantastic descriptions of the canyon and rafting. Looking forward to more from this author
254 reviews1 follower
September 25, 2024
Thriller at the Grand Canyon! Audiobook Review 🎧
I love all of these Forensic Geology books and this one is no exception.  Cassie and Walter have a unique skill and get called to the Grand Canyon to help solve a mystery of a stranded raft with no people in it.  I enjoy listening to how they figure out the story behind everything and are able to follow the trail to try and solve the mystery.  Having the backdrop be the Grand Canyon this time was a lot of fun to listen to and take in the surroundings. This was a very enjoyable book, but the story and how everything wrapped up didn’t draw me in like the last few books had so I couldn’t give it 5 stars.  I do look forward to listening to the next book.  I thought Nellie Scott did a great job with the narration of the book and made it great to listen to. #AudiobookObsession #TheFlock
929 reviews3 followers
October 22, 2024
Workmanlike Novel

I don't have any specific words of praise for this novel and no deficiencies egregious enough to stop reading, so I gave it a middle-of-the-road rating. The only character I warmed to was Pete Molina, the park ranger. Walter and Cassie, presumably the only recurring characters, seemed to be merely the vehicle by which Dwiggins tells the story. The plot was clever and engaging. The geology of the Grand Canyon was explained well and was my favorite part of the book. I thought the pace was slow for a mystery/thriller. I kept wishing they would get on with it already. I also wished for a description of the makeshift geology lab and some idea of the testing the geologists did there. I don't know whether I would read another book in this series.
Profile Image for Debby Bonk.
14 reviews
March 14, 2021
Adventure, Mystery and Drama in the Grand Canyon.

I really enjoyed this book, could hardly put it down, so many twists and turns in the story that kept you guessing and then guessing again. Beautiful fascinating verbal views of the Canyon, fascinating history, exciting descriptions of river rafting and trying to beat the river and the canyon. The author brought forth the threats to the river while writing a fascinating story to keep my interest. The characters were varying personalities that added that extra color to the story. Read this book, become immersed in it, it is time well spent.
19 reviews
December 6, 2022
This was not the greatest book I've ever read. I so wanted to like it because I love science, I love the Grand Canyon, and I love mysteries. I thought this book would be perfect for me. But I was mistaken. I felt like it was very disjointed and at times hard to follow. There seemed to be storylines that were unnecessary and just made the story more convoluted. I felt like some things were not explained well. One character disappeared and was 'missing' but then suddenly reappeared with little explanation. It was confusing and hard to follow. I may read another book in the series just to see if things get better, after all this was the first one.
Profile Image for Lisa.
3,747 reviews21 followers
August 14, 2024
Another amazing book in this series! I love the backdrop! The author does an excellent job showcasing this wondrous place. Then add in all the complex characters we run across as well as the ones we know and love. I will say this makes me hesitant about taking a river raft trip down the Colorado river.

This mystery really has a twisted tale that is told exceedingly well. I was drawn to the landscape, the characters and the compelling storyline. I listened to this is one sitting. Nellie Scott does a wonderful job portraying all these characters. Men, women it doesnt seem to matter. She is pleasant and easy to listen to. I look forward to more in this series!
51 reviews1 follower
May 28, 2025
Stratigraphic action on the Colorado River

Toni Dwiggins seems to have written the Forensic Geology series especially for me: a geologist and mystery reader both. Seldom does geology feature in any fiction book, and here is a whole series to enjoy. River Run is the first I’ve read. The action is relentless; disappearances and bodies multiply; the main suspect is frustratingly enigmatic; and the real-life issue about water decline in the West looms seriously over all. The stratigraphy, key to the plot, is well explained, though a stratigraphic column diagram would be helpful to readers who favour white-water rafting and back-country hiking over geology.
Profile Image for Carol Palmer.
22 reviews2 followers
April 26, 2022
Great Story . Wonderful Twists and Turns


Having a Earth Science family, with a geologist, environmental scientist, and a earth science chemist, to name a few, this book " Rocks." Shooting the rapids to find the clues is a good introduction to the rocks and minerals of the Grand Canyon as well a a wild ride down the river. Unfortunately the abuses, by man, of the Colorado are all true . Take some time and pull up Lake Mead on the computer and see how low it is! The other books in this series are recommended as well.








Profile Image for Patricia Moynihan.
15 reviews
November 18, 2022
Love a good mystery

This is the first time I've had the pleasure of reading a mystery involving forensic geology. I'll have to admit to being skeptical at first but this was an excellent story. The Colorado river is as familiar to me as my own backyard but the geology element in this story makes me want to get back out there and take a deeper look at the geology. The story stands on it's own as an excellent mystery and murder mystery. Looking forward to reading the next book.
Profile Image for Gazelle.
811 reviews10 followers
August 21, 2024
Forensic geologists Cassie Oldfield and Walter Shaws are about to take us on a wild ride. I really had no idea what was going to happen next and who twists kept coming. What a thrilling mystery that will have you guessing who is the bad guy or is there more than one? Lots of personalities/characters and relationships that you get to figure out! Nellie Scott did a good job narrating and I really enjoyed listening to this one. First book by this author that I read/listened to.
Profile Image for Jocelyne.
4,867 reviews21 followers
October 18, 2024
This is the fifth book in the Forensic Geology series. I like this series! Cassie and Walter's new adventure is suspenseful, and entertaining, filled with intrigue, danger, and twists and turns. The story is complex, and captivating. The scenery is breathtaking. The writing is imaginative, and enthralling. Nellie Scott did an excellent job bringing these characters, and this story to life. Looking forward to listening to Lands End, the next book in the series. #PFPAudio
Profile Image for Kit.
1,517 reviews16 followers
March 24, 2021
Read: DNF
Rating: 1,5 Stars

At 5% read I feel like I cannot really rate this but I'd give it a 1,5, 1 Star for the idea, since that's really awesome, it's the execution that doesn't work for me.
This feels dryer and harder to get trough than some really freaking wordy scientific texts.
I so wish this would have been good.
3,063 reviews45 followers
August 19, 2024
I loved the narration of Nellie Scott

We find our Forensic geologists Cassie and Walter are in trouble this time on or in the canyon's Colorado River. Having to use their skill, but with rafters going missing and being stranded, and using pebbles. These two find it not only rafters in trouble but the river is in danger.

A great mystery thriller.
67 reviews
January 4, 2020
Engrossing

I enjoyed the enthusiasm of the characters for their field, even if I didn't understand some of the specifics. A good, interesting well-being paced story. Description of the experience of river rafting was good.
89 reviews1 follower
September 24, 2020
Interesting read

With an undergraduate degree In Geology the premise of forensic geology piqued my curiosity. Enjoyed the book I'm familiar with the cartography covered I hiked part of it, and the book brought back memories.
45 reviews
April 6, 2021
Disappointed

Way too much detail that I really didn't care about. I just could not get into any of the characters. The only
one I found interesting at all was Becca's struggle to survive. Truthfully I skimmed through most of this book, just wasn't for me..
Profile Image for Steve Thomas.
728 reviews5 followers
May 22, 2021
The Grand Canyon like you've never seen it

What an amazing story. Heros and villains play their parts masterfully. The geology of the Grand Canyon along with white water rafting make this a compelling pages turner.
Profile Image for Linda.
2,174 reviews
September 24, 2021
I have read all five books in the Forensic Geology series, beginning in October 2018. All of them have been dramatic, interesting, and educational. I hope Ms. Dwiggins will be writing more volumes in the future.

** HIGHLY RECOMMENDED **
8 reviews
September 18, 2022
Only for rockhounds

Only reason it got 2 stars is because I love the Grand Canyon. I've hiked it twice. This book was beyond informational as far as geology buffs go, but for the average person it was quite the drag. Plot not that interesting.
99 reviews
September 30, 2022
WOW!!!!!

Very interesting geology...how the forensics can solve mysteries...crimes...greed, etc. The plot is fascinating...leads into real worries here in the West...WATER. Well written!!!.
7 reviews
June 11, 2023
This book, as well as the previous three, was excellent! I am not a geologist, but enjoyed reading about how geology can pinpoint crime! Fascinating characters, never ending action and well thought out plots keep you engaged! The series is over and I want more!! Great job writing!
60 reviews
July 15, 2023
A good story

I enjoyed this book. I really got into it when they were rafting and discovering all the layers of limestone. A good story intertwined with information.
I never knew anything like what's in this book about the Grand Canyon before, and I Googled a lot as I read.
54 reviews1 follower
December 9, 2023
my favorite author ever!

The best book in my favorite series ever! Way to go Toni Dwiggins. I thought you had quit writing and was so glad when I saw a couple more books in your series. Please never stop writing!
Displaying 1 - 30 of 48 reviews

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