The 39 Clues is a series of adventure novels written by a collaboration of authors, including Rick Riordan, Gordon Korman, Peter Lerangis, Jude Watson, Patrick Carman, Linda Sue Park, Margaret Peterson Haddix, Roland Smith, David Baldacci, Jeff Hirsch, Natalie Standiford, C. Alexander London, Sarwat Chadda and Jenny Goebel.

The first story arc concerns Dan and Amy's quest to find the 39 Clues, which are ingredients to a serum that can create the most powerful person on Earth.

Each book chronicles one location which Amy, Dan, and their au pair Nellie Gomez travel to and focuses on one historical character associated with a Clue.

At her funeral, her lawyer, William McIntyre, gives Dan, Amy, and some of their other relatives, a choice between one million dollars and a chance to participate in the Clue hunt.

After convincing their au pair, Nellie, to chaperone their trip, Amy and Dan travel to Paris, where they follow a trail of cyphers and traps that lead them to the catacombs under the city.

Amy's internet searches lead to the probable location of the second Clue: Vienna, the home of the famous Austrian composer Wolfgang Amadeus Mozart.

En route to Vienna, the Holts try to steal the lead to the second clue from Amy, Dan, and Nellie, only to find it torn to shreds by Saladin.

A pair of tungsten swords from Venice leads Amy, Dan, and Nellie to Japan for a clue related to Japanese warrior Toyotomi Hideyoshi.

Dan and Amy head to Sydney, Australia, to learn about what their parents knew about the 39 Clues from their dad's cousin, Shepard Trent.

Dan and Amy reunite in Tingri, China, and fly up to Mount Everest in an experimental helicopter where they find a Janus vial left by British mountaineer George Mallory.

Meanwhile, Natalie Kabra recounts how she had been experiencing nightmares for a week about Dan and Amy almost dying while being pushed to a propeller by her mother Isabel, and there is no sound except for laughter.

The mystery man reveals his true identity as Fiske Cahill, Amy and Dan's grand-uncle and Grace's younger brother.

The second recounts the life of Gideon's daughter, Madeleine, and her attempt to reunite the Cahill family, protect her father's ring, and outwit Damien Vesper from acquiring it.

The third tells of Grace's first mission to Casablanca, as she competes against Vesper agent General George S. Patton to retrieve Gideon's ring.

After meeting Dave Speminer (a friend of the Rosenblooms' mother, Astrid), Atticus remembers something that his mom said to him before dying: Missing Voynich with LaCher.

At the Falls, a second attack occurs, and a blow dart coated with curare hits Dan, but a nearby doctor saves him from the poison.

A taxi driver takes them to Mabu Thermas Hotel and Spa and sees Dan's new wallpaper on his laptop, one of the "plumbing pictures" in the Voynich.

He believes that to combat a doomsday device, he needs the serum which he recently created, and he drinks an unknown liquid an Ekaterina scientist manufactures.

Following a clue from Astrid, Amy and Dan go to the National Museum of Natural History, which houses the largest collection of Lewis and Clark items.

Evan and Ian receive a call from Phoenix from a motel in Washington state and head there with Hamilton and Jonah, whom Sandy, Casper, and Cheyenne follow.

En route, the hostages break free and incapacitate Sandy, Casper, and Cheyenne and meet up with Amy, Dan, Atticus, and Jake.

The first novel, Nowhere to Run by Jude Watson, was published in 2013, followed by Breakaway by Jeff Hirsch, Countdown by Natalie Standiford,[25] and the last book, Flashpoint by Gordon Korman,[26] in 2014.

This makes the siblings to go to a safehouse in Ireland where they find a book written by Gideon's wife Olivia, which contains the serum's antidote.

As the group discusses the riven crystal and Tikal, a national park and archaeological treasure uncovered in 1956, the chopper suddenly shakes.

Meanwhile, in Trilon Laboratories in Delaware, Nellie Gomez, acting as Nadine Gormey, makes contact with Sammy Mourad, who is being held in the building to improve the serum for Pierce.

However, even though the riven crystal is found, Dan is abducted, Pony is killed by Pierce's thugs, and Nellie and Sammy are captured at Trilon Laboratories.

They Cahills travel to Amsterdam and discover that the Outcast is planning to detonate a lost nuclear bomb in the North Sea, overflowing the canals of the Netherlands and causing extensive flooding.

[39][40] In the last week of December 2011, the Scholastic editorial team released seven short stories as part of The 39 Clues: Rapid Fire e-book series.

[45] An editorial team in Scholastic came up with the idea of an interactive series with online games and asked Rick Riordan to write the first book.

[46] Riordan agreed because he thought it was a good idea, and as a middle school teacher he loved making history enjoyable for younger readers.