SKU: 88874106722

The sign of the five (Improbable Tales of Baskerville Hall, Book 2)

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Description

The sign of the five (Improbable Tales of Baskerville Hall, Book 2)In the second thrilling installment to the Improbable Tales of Baskerville Hall series, Arthur returns to the elusive Baskerville Hall and must solve the mystery behind a poisoned Sherlock Holmes, facing new threats, harrowing challenges, and ghastly ghouls along the way. It's time for a new adventure, are you ready? When Arthur Conan Doyle returns to Baskerville Hall, a secretive school for extraordinary students, he's excited to begin winter term

In the second thrilling installment to the Improbable Tales of Baskerville Hall series, Arthur returns to the elusive Baskerville Hall and must solve the mystery behind a poisoned Sherlock Holmes, facing new threats, harrowing challenges, and ghastly ghouls along the way. It's time for a new adventure, are you ready?

When Arthur Conan Doyle returns to Baskerville Hall, a secretive school for extraordinary students, he's excited to begin winter term with the friends he loves. However, soon after his arrival, a dangerous foe threatens his favorite professor, Sherlock Holmes, and all signs seem to point to a force that Arthur had hoped he'd seen the last of... the Green Knight. But Sherlock isn't the only target; others begin to fall prey as well. The question is: how are they all connected?

In the ultimate race against time, Arthur will have to dodge old enemies, befriend new faces, and brave encounters with spirits to solve the mystery before it's too late. But there are more puzzles to solve than one; it seems a new term at Baskerville Hall may not only test Arthur's wits... but his friendships too.

Praise for the Improbable Tales of Baskerville Hall:

"At the top of the most intriguing school list, with Hogwarts and the School for Good and Evil." -Kathryn Lasky, Newbery Honor author

"A tantalizing playground for inquisitive minds." --Publishers Weekly (starred review)

"A well-paced, exciting story in which stalwart heroes attempt to outwit inscrutable villains...Readers who love period mysteries and adventure stories are sure to enjoy." --ALA Booklist (starred review)

"A bold and thrilling reimagining of Arthur Conan Doyle's early life, filled with students and teachers who the world would later come to know so well, including Dr. Watson, James Moriarty, and, of course, Sherlock Holmes." --The Conan Doyle Estate

An Amazon Best Book of the Month!

A Junior Library Guild Gold Standard Selection!

Publishing in over 25 languages!


One poisoned professor. A mysterious returning villain. And a school where everyone has a secret.


  • A Thrilling Middle Grade Mystery: A young Arthur Conan Doyle must use all his wits to solve the case of his poisoned professor before the clock runs out.
  • A Sherlock Holmes Reimagining: See the world's greatest detective not as a master investigator, but as a beloved teacher in terrible danger.
  • Boarding School Adventure: Explore the corridors of Baskerville Hall, where ghostly ghouls and ancient secrets wait around every corner.
  • Found Family and Tested Friendships: With his friends at his side, Arthur must face down old enemies like the Green Knight, but the biggest threat might be to their own loyalty.
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SKU: 88874106722

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ODemi
Bozeman, US
★★★★★ 5
Very pleasant nano hydroxyapatite toothpaste.
Color: A - Magic Mint (Pack of 3)
Bought this new nano hydroxyapatite toothpaste free of fluoride. This is a new technology toothpaste that reinforces enamel. The Mint taste is very pleasant.
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Reviewed in the United States on May 20, 2026
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Clashmore
Battle Creek, US
★★★★★ 4
Pineapple and papaya
Color: A - Magic Mint (Pack of 3), Color: A - Magic Mint (Pack of 3)
I like it okay. I will use all of it but I am unsure if I will buy it again. It foams very little. I feel like I use more than I do with other pastes/gels. My mouth feels clean without having that too minty/medicinal taste from traditional flouride pastes. It comes out of the tube easy and sticks to my brush. I didn’t know until after I purchased it that there is papaya and pineapple extracts. There IS a photo in the product description that says this and I neglected to click through them all. I have two members in my household that are allergic to those ingredients so I have not had them try it. The only taste is a mild mint though. I think the whitening effects of nanohydroxyapatite pastes is much better than other popular brands that boast “whitening.” My teeth simply look whiter and shiny.
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Reviewed in the United States on September 22, 2025
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JOHN V. PENA
Cuba, US
★★★★★ 5
GREAT CHOICE !!!
Color: A - Magic Mint (Pack of 1)
Definitely works as discribed helped with tooth sensitivity active ingredients help whiten and strengthen tooth enamel. I alternate 3 X a week woth normal Fluoride toothpastes and use this 2X a week. Total game changer
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Reviewed in the United States on May 21, 2026
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Tiywilli
Phoenix, US
★★★★★ 5
Perfect
Color: A - Magic Mint (Pack of 3)
This is the only toothpaste I use now. It makes my teeth look great, tastes great & does exactly as intended.
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Reviewed in the United States on June 2, 2026
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David P
Dallas, US
★★★★★ 3
And alternative to floride toothpaste.
Color: A - Magic Mint (Pack of 1)
I've been using this alternative toothpaste for a couple months now. It's expensive compared to regular toothpaste, but some suggest that it's healthier for your teeth. Nano hydroxyapatite is supposedly the same molecule that our teeth are made of. So perhaps it may be better for hardening teeth than fluoride. Of course, I can tell if it is doing that or not. Do your own research. It's a bit more fluid than standard paste, so it sits more flat on the toothbrush. I've discovered that if it dribbles from your mouth onto your shirt, it leaves a white stain on the fabric! So don't use it while wearing your good work shirt. The taste is more mild than the usual minty toothpaste. Not bad at all. At my next dental exam we'll see if it's cleaning my teeth effectively.
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Reviewed in the United States on November 24, 2025

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