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Never turn your back on the Cahills . . . The most powerful family history has ever known returns with a vengeance in The 39 Clues: Doublecross!

The Cahills are the world's most powerful family, but their strength is being tested. A sinister man calling himself The Outcast has targeted the family and set them an impossible test. He's recreating four of history's worst disasters and challenging the young Cahills to find and stop the tragedies before it's too late. Now, with one disaster behind them, siblings Dan and Amy Cahill and their friends have just days to discover what the Outcast's next move will be.

Their frantic search seems to be pointing toward a terrifying air disaster, the explosion of the Hindenburg airship. But no one travels by airship anymore -- what do the Outcast's cryptic messages mean? The young Cahills must split up and take to the skies to try to find the answer . . . before their whole world comes crashing down.

195 pages, Kindle Edition

First published July 28, 2015

84 people are currently reading
2038 people want to read

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C. Alexander London

36 books211 followers

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5 stars
2,209 (54%)
4 stars
1,028 (25%)
3 stars
666 (16%)
2 stars
118 (2%)
1 star
58 (1%)
Displaying 1 - 30 of 106 reviews
Profile Image for Edy Gies.
1,375 reviews10 followers
February 26, 2016
I would rate the action of this book as okay, but over the top. Jumping out of a blimp that has almost reached the Karman Line is unrealistic, but my son thought it was awesome. I was surprised when one of the characters "came out" as being gay and that was made a big deal. I don't like boy/girl relationships in children's books as I believe they are unnecessary, but I especially don't agree with adding boy/boy relationships to the plot, as it accomplishes nothing plot wise other than getting the author's views out. This is supposed to be an adventure story, not a relationship story anyway.
Profile Image for Raymond Richard .
217 reviews
September 16, 2015
I am ashamed of all the bigots who don't like this book bedsit mentioned that one character is gay. You're ok with all the violence and murder but you mind that a boy dates a boy? 3 sentences in a book should not cause so much offense. I'm offended you're offended.
Profile Image for Christian Schultheiss.
582 reviews19 followers
May 9, 2025
I’m a bit torn with this next continuation in the third 39 clues spinoff series. On one hand this had some intense action and well written descriptive scenes, mixed with some of the truly most elaborate and creative settings and plot placements that the family has ever done while still seemingly with the realm of this universes reality. All that positive mixed with the negative that this is definitely a shorter book and aside from the actual tension and Hamilton coming out (which was surprisingly impactful) there just wasn’t much overall plot moving forward or just really much substance at all for at least thirty percent of the book. I’m still interested to see what another Alexander London clues book could look like but he definitely has to take notes and improve the entirety for me and if he does I’ll be the happiest camper. 3.5/5
252 reviews
October 10, 2015
I really have not liked this new series of the 39 clues and don'r plan on reading any more of them. I especially disliked this book and will probably throw my copy in the trash. I don't understand why the author thought it acceptable to make Hamilton Holt gay. Totally inappropriate especially for children's book. Just because other authors think it is acceptable to write about doesn't make it right, especially when the target audience is so young and impressionable. Don't let you kids read this book. Totally inappropriate!
Profile Image for Rustic Red Reads.
483 reviews38 followers
July 13, 2015


Thank you Edelweiss for providing an e-ARC of this book.

So it's the second book to the fourth series (or third spin-off of The 39 Clues) and the 37th book, BTW.

So the disaster that the Outcast will be replicating is Hindenburg, the zeppelin that ended the airship travel. So this is probably the (or one of the...) realistic book in the series so far and better than Mission Titanic.

It first started when the Outcast sent a poem to Amy and the others pertaining to painting about the death of Icarus (wherein the people are not looking at Icarus but to the sailing boat) which means There's a lot of red herrings in here. Plus we have scenes of Nellie and Sammy trying to infiltrate .

The parts of the stories will include and some revelations: a) something about Hamilton Holt;
b) the Outcast plans; and
c) the identity of the Outcast

Plus there is a Filipino character here named Eriele Cienfuegos (probably named after his reader), which have a huge part in this book. Can't wait to read the next book in the series, Mission Hurricane.
Profile Image for Kyra.
174 reviews
Want to read
July 22, 2015
FINALLY THANK YOU LORD :') PLANNING TO READ THIS ON SAT WHEN I'M NOT BOMBARDED WITH SCHOOLWORK (first day of school, there's homework already bless)
Profile Image for Tarissa.
1,580 reviews83 followers
August 28, 2017
What I liked? A fast-paced adventure filled with fatal intrigue. Plus, Dan starts showing off his inner geek that's been there all along (good for you, Dan!). The stakes (and the dirigibles) are high. Oh, and the scene where someone from the Cahill family falls from the sky.... whew!!! My, my, that is an incredible moment.

What I didn't like? One of the characters revealed that they are gay. This was a completely unexpected twist, and one that I wasn't thrilled by. Just saying. The topic came up maybe three or four times in the book in passing, but wasn't discussed in much depth.
Profile Image for Esther.
19 reviews
May 2, 2020
I didn't enjoy it as much as other books in this series, however I loved Hamilton's sudden coming out and how easily all the other characters took the news (unlike all the bigots above and below). Diverse characters in children's books are needed, especially when defying stereotypes.
However small mistakes were annoying and took me out of the story, such as "Los Angeles shimmered in the heat of midday. The sky of Los Angeles was turning gold and red with the sunset." on page 6 - which is it midday or sunset? How did nobody spot this in proof reading before publication?
Even worse was the description of the "candy-coloured spires of the Kremlin". The Kremlin does not have candy-coloured spires, that's St Basil's Cathedral next to the Kremlin. It is an easy mistake to make, but more upsetting as I usually really enjoy learning about different cultural sites from around the world in these books and this has now made me doubt the accuracy of all the others.
Profile Image for Grant.
14 reviews1 follower
January 12, 2016
"Mission Hindenburg" by C. Alexander London is a great novel with so many twists and turns that you'll never know what happens next. This book is the second in the series, the sequel to the first one, "Mission Titanic." After the "Outcast's" failed Titanic plot, he tries to recreate another disaster, the fiery Hindenburg crash. In the beginning of the book, Ian and his friends get a message from a blimp. The blimp starts flying toward its landing spot, and the kids follow it. Once the blimp lands, it blows up, but the kids got there at just the right moment, and prevent any injuries to innocent people. However, they believed that the explosion wasn't the disaster the "Outcast" was trying to recreate, they believed that he was just showing them what he was capable of. After some research, they find that a zeppelin race will be held in Athens, Greece, and the racers will be racing to the Karman Line, which is the edge of space. During the race, all the zeppelins had to land because of a mishap caused by one of the kids. After this, only two zeppelins remained, and one was a zeppelin the kids knew wouldn't be attacked, so they stowed away on the other one. Once aboard, they meet a girl who tries to tase them with a taser. But the kids fought back, and they eventually captured the girl. However, I can't spoil the book, so if you want to know what happens your just going to have to read it.
Besides all of the action and adventure, I feel that this book was very well written by C. Alexander London. He did a great job of describing the setting of the book throughout the novel. I really feel like I could have been there while I was reading the story. Another thing that London did well was portray the characters as they actually would've been real life. In "Mission Titanic," I feel like the characters never had too much urgency. For example, first the kids travel to Canada, then to Boston, then to Argentina, and then they finally reached where the actual disaster was happening, and yet they were still a little too calm. However, I didn't really notice this until I read Hindenburg, then I noticed there was a huge difference in the characters. In Hindenburg, the kids started off in L.A., and then flew directly to Athens. One kid even went to jail because he was trying to stop the disaster. I feel like the same kid in the last novel wouldn't have done that.
I really liked this book. It was so interesting and there was the perfect mix between fictional and nonfictional elements. I predict that in the next book, the "Outcast" will try to create another disaster, but the kids will foil his evil plot and save the day. I feel that C. Alexander London did a very good job, and I also feel that this book deserves all 5 stars. :)
Profile Image for Snigdha Thatikonda.
41 reviews20 followers
February 13, 2016
This was, by far, one of the best books in the series! So much stuff got laid down, like the fact that Grace was not at all who she seemed, Cara is an amazing character, and Dan cannot stop being awesome! I can't find anything wrong with this book!
And the fact that I was right about who the Outcast is, also helps.
And I came up with that theory after a no-good-fanfiction boredom session and being delusional because of not getting enough sleep! How amazing is that!
But seriously, pick up this book, because C. Alexander London did an incredible job on this one!
Profile Image for Alberto.
152 reviews
August 14, 2016
Another amazing book on the 39 Clues series. I loved the ending and I'm pretty sure that what I'm thinking is too obvious to be what is going to happen.

10 reviews
October 25, 2015
The book started the same way the last 20 books have - a rich and powerful man is thinking about how to finally defeat the Cahills. He always gives them little clues on how to finish his seemingly impossible task. It is becoming predictable. Especially if you are a fan of the 39 clues series 1 2 and 3, this may come across as uninteresting - everything has been done before. The main characters always make it out.

If you haven't read other 39 clues books, read series 1: the Clue Hunt, and series 2, Vespers vs. Cahills and nothing else!!
Profile Image for Cas ♛.
1,013 reviews127 followers
February 8, 2016
Great MG. Not doing a review for it as usual though. If you want to ask something just comment :)
Profile Image for Karsyn .
2,365 reviews44 followers
May 4, 2016
Good one. Good story, glad they finally figured out what I did last book. :) Such a cute overall series.
208 reviews2 followers
September 15, 2016
What can I say? Call it a guilty pleasure, but I am enjoying this series even though I am not in the authors target demographic.

It is a quick, fun, easy read (or listen)

4 stars
Profile Image for Angela Massengale.
102 reviews3 followers
January 23, 2017
Have to admit--not loving this series of 39 Clues books. Going to stick with them, but my ratings of each one seem to be dropping with every book I read...
Profile Image for Hanne.
682 reviews59 followers
April 24, 2017
OKAY SO WHYYYYY ???? UGH EW NO SORRY GBYE (even though I'm still going to finish the series,but REALLY HOW WHY)
365 reviews
January 21, 2023
I was a little surprised when these children’s books included murder. With this one they’ve included other controversial issues. Matt 18:6
2 reviews
March 21, 2018
The Book The 39 Clues (DOUBLECROSS): Mission Hindenburg by C. Alexander London is about Ian (the former leader of the powerful family of Cahills) and his friends trying to stop the Outcast from re-creating the Hindenburg tragedy. I enjoyed this book even though it’s slight vagueness in the description of the setting in certain moments.

Personally, I liked the conflict because of how much it makes me have the feeling of no exit from the situation at hand. For instance, Ian and some of his friends are in Athens, Greece, there are multiple blimps they look into and they don’t know which one will explode and they are not in control of the blimps. So that definitely gave me feelings of suspense and anxiety in the greatest way. Another instance is when Nellie and Sam (Also Ian’s acquaintances(as he would say)) are in Moscow, Russia in a Lucian base and they are looking at Lucian records for information on the Outcast. They are not somewhere they are in any way welcomed, and if any Lucian (or enemy of them) finds them they will surely be tortured or killed. Which furthermore gives me a feeling of suspended peril and anxiety.

However, the setting was a little vague to me. For example, when Ian and some of his friends are in Athens, Greece, they only described what was eventually interacted with or necessary for the plot in the setting, in this case, the ancient ruins and the giant blimps. But the very rare (but very helpful) pictures in this book helped describe what the characters were dealing with and it helped me piece the setting together adding more thought-provoking ideas in my mind.

I liked this book because of the suspense it showcases. And it is good to have a slightly less described setting because it lets my imagination fill up will possibilities that will/might affect the character’s situations. This book might not appeal to people who don’t like or disapprove of spy movies/books. Or if you don’t like anything with little to a lot of suspense and peril. Outside of reading, you can find this adventures similar to this in a James Bond movie, or in movies with a lot of action and suspense. This book has very little romance (if you include mild flirting romance), so if you like a good story with action and drama, then this a highly suggested book for you.
Profile Image for Chalinviri .
455 reviews
July 10, 2023
📖Misión Hindenburg📖

Ok ok, esta saga parece que quiere hacer unas enmiendas por el desastre de la Saga anterior (La verdad, no se porque fue tanto drama y exageración)

Aqui seguimos viendo las peripecias de Ian Kabra como líder Cahill ahora con una misión a cuestas: los adultos Cahill creen que no se debe dar tal responsabilidad a niños (hasta ahi estoy con ellos), pero su forma de respaldar su punto es un tanto exagerado, y extremo...que es eso de recrear desastres y obligar a los niños a impedirlos limitándolos en recursos. de los niños)

Bueno...a pesar de eso, por fin estoy viendo un poco de madurez en los niños que llevaba esperando desde Vespers y aunque ahí evolucionaron un poquito, esperaba seguir con eso en Unstoppable y no pasó!!!
Mientras que el libro anterior se recreo el desastre del Titanic, este libro nos contó un poco del Hindenburg, el Zepelín que explotó y también descubrimos el guilty pleasure de Dan: Viajes espaciales.

Realmente ver las interacciones de Jonah, Hamilton (Quienes son best friends por cierto...y tan opuestos), Dan, Amy y hasta del propio Ian es buenísimo, c/u tiene un carácter de la fregada y organizar un montón de adolescentes o Jovenes adultos y detener los desastres de un anciano caprichoso, es interesante de ver.

De verdad, con cada libro de Doublecross que leo, mas afirma la idea de que la Saga anterior no tienen nada de conexión con la historia...

Esperemos que en los próximos libros sigamos un poco con esta linea y no tanto con unstoppable por favor.
Profile Image for Kryssy.
764 reviews3 followers
August 6, 2024
If we have another person double cross… i get that it’s the same of the series, but dang… that’ll get old

I don’t know as much about the Hindenburg event than I do about the Titanic. I wish a bit more background was given about the even (and the historical figures in the original series). Especially considering the target audience, school curriculums may not have gotten to some of these yet

A couple things felt pushed, a few things I want to know more about, and some things are talked about way too much. This series really needs to work on pacing

- Outcast took control of cahill funds. Amy and dan are surviving off of jonah’s income
- New riddle about flying while a blimp is overhead
- Hamilton is gay? Seems a little bit of a stretch just to include LGBT. The sisters have much more of a gay-vibe
- Introducing important cahills that we never got to know. Irina’s brother and grace’s husband
- Lucian onboard helps amy and dan
- Grace asked irina’s father to kill her husband
- Dan goes skydiving and all chute deploys are not working. Ends up setting 3 records. That no one can know about
- Cara is kind of jealous of ariel
- Ariel is the double crosser. She was about to jump out and break dan’s “record.” Ian tazed her
- Grandfather is alive
- Exclusive: grace’s husband hopes having a kid isn’t a liability
This entire review has been hidden because of spoilers.
Profile Image for Sally.
Author 23 books141 followers
September 8, 2018
Another whole series review.
191 reviews1 follower
March 7, 2024
Another great installment

Love that the 39 clues team let Hamilton be gay, and I love that Dan made no less than 2 jokes withing 24 hours of his coming out.

Love Jonah wanting to abandon the gangster facade and pursue more artistic endeavors. Kind of sad that a lot of characters don't get it, but I see his vision.

Love Dan's realization of responsibility towards the Cahill family when he's seconds from free falling to Earth. It kind of opens back up his character arc from the precious series and shows us a bit more of him along with the space stuff.

Love Amy's brief callback to her stuttering in series 1, when they're locked in the supply closet. We're still very in touch with who she is and how far she's come.

Overall, you can tell that this installment was written by someone who understands these characters.

The Ian / Kara bit is a bit trying for me, and the Outcast mystery felt like it went nowhere-- we learned no more than we did last book, aside from the bonus material at the end. Those are my only complaints.


I've been re-obssesed with Landscape with the Fall of Icarus lately and I'm glad I reread this to remember where I initially saw it.
This entire review has been hidden because of spoilers.
Profile Image for Juee Dhar.
95 reviews10 followers
March 21, 2021
It was quite refreshing coming back to a book series that was basically my entire middle school wrapped up into a neat pile of books. I must admit, after reading 20 ish books of the series, I have lost my original enthusiasm to read them. But still, a good read, and Ian - Cara moments make me grin. The character development we can see from the very first book to present (anywhere the book refers to Irina Spasky and I am transported to me reading the first few books of the series back in 2014) is remarkable, the subtle shift to soon becoming adults is fun to observe. (also the book introducing Ham as a gay character, without any stereotypes attached made me very happy (and proud to be a part of the 39 clues fam))
Fav moment = The meeting with V Spasky was completely a wildcard and that is possibly my only motivation to complete the doublecross series, because now I just need to know... who really was Grace Cahill ?
Profile Image for Yukiraking.
324 reviews3 followers
June 1, 2020
I have to say that I'm incredibly satisfied with how this one ended.

Also, there was a section towards the end, but kind of the middle, where everyone is split up, and we're only given the perspective of one at a time, and we don't know who's in danger, or who might get caught, and I have to say I loved the way that was formatted. It really built the excitement for me. Dan had a particularly interesting point in this book, stunt-wise, that I really liked, and Vikram Kabra finally made an appearance!

Vikram and Madison Holt are the two characters that I most wanted to show up (because it just didn't make sense not to include them at some point) and the fact that Ian is currently in charge of the Cahill's really just made it the perfect time for him to show up. I'm incredibly disappointed that Madison didn't show up, but this is enough for me.
Profile Image for Fatima Sarder.
533 reviews1 follower
June 6, 2022
“It is hard when our heroes fall, yes?"
― C. Alexander London

No continuity. In the previous book, Nellie was supposed to have been taken hostage, that plot is abandoned without any explanation whatsoever.

The action is a bit over the top and unrealistic. An untrained boy falling from space who somehow miraculously survives and goes on to prevent another disaster without missing a heartbeat? Yeah, no.

Also the entire mystery and apparent ruthlessness of Grace Cahill is slowly inching towards the light.

Profile Image for Somnath Roy.
69 reviews17 followers
July 30, 2022
A pretty well written adventure with notes of deception despite all cards being on the table.

Some good action sequences in a book that focuses heavily on Ian Kabra and his psyche as he struggles with being a leader to the Cahills after being Outcast from his position of power.

It also has some dark and stunning revelations to the thickening plot and thus far, the story has all the makings of a good thriller.

Glad to see things pick up quality like this after the disaster that Cahills vs Vespers was.
Profile Image for San To.
75 reviews3 followers
May 16, 2025
Not bad. I would say almost amazing even among the 39 clues ranks except for one flaw for me.


SPOILERS

The authors seems to think leadership is having orders never questioned? At the start I was thinking Ian eventually learns leadership is not that, but then it turns out the other members learns it's exactly that.

SPOILERS



But other than that, one of the better ones among the non-original authors. Character driven adventure and action.

Overall, 5 starts, because a decent 39 clues story really hits my adventure bone.

This entire review has been hidden because of spoilers.
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