|The Viper's Nest|
|Publication Date:||February 2, 2010|
|Setting:||Johannesburg, South Africa,|
|Preceded By:||In Too Deep|
|Followed By:||The Emperor's Code|
|“||"I wanted him to die, Dan. I've never felt that before. What's wrong with me?'"||”|
— Amy Cahill, about Alistair Oh.
Shocked by the death of Irina Spasky, Dan and Amy march into danger once again. For the first they begin to question how much they trust their au pair, Nellie. Later in the book, she regains their trust.
The search begins the morning after the fire that killed Irina Spasky. The two were shaken by what had happened and they could not believe that Irina was on their side. A few moments later, Nellie appeared, signaling the arrival of the police. It turns out that Isabel Kabra had called the police and put the blame of Irina's death on Alistair.
Meanwhile, after using their code-breaking abilities, Dan and Amy figured that the last words Irina spoke was actually a song. "I'm with you and you're with me and so we are all together", which points them to their next destination: Pretoria, South Africa.
Upon their arrival in South Africa, a mysterious man hands a postcard to the siblings which points to a connection to a famous person called Shaka Zulu. As they unravel the history of Shaka Zulu, they find out that he was a member of the Tomas branch. Following a line of Clues, Shaka Zulu was then connected to Winston Churchill.
While visiting a library with a document written by Churchill, they discover that the Clue was hidden with the body of Shaka Zulu. They also find a tunnel in which, it is said, that Churchill had hid while he was in Africa. They unlocked the message of the Churchill which pointed to a certain coordinate which turned out to be a Tomas stronghold. After infiltrating the Tomas stronghold they soon discovered a box with a diamond in it. While at first they thought that was the Clue, Aloe, which had been growing around the box, turns out to be the real Clue.While leaving South Africa, Dan and Amy were captured by the Kabras. They were about to kill Dan when suddenly a professor, (who helped them at the Tomas Stronghold), saves them again. They escape together with what Dan thought was the vial of green liquid that they thought was their lead to the second Clue in the Maze of Bones. They escape by flying Grace Cahill's old plane, The Flying Lemur. During the ride, Dan and Amy have a little quarrel, accidentally breaking the vial and spilling some of the contents onto Dan's arm. It turns out to be a Kabra poison. To get the antidote to save Dan, they fly to Grace's home in Madagascar.
While at Grace's Madagascar home, where they learn the Clue is Aloe, they find a page in her journal that says, ″I am feeling melancholy today, thinking about my dear A & H and missing them so. I cannot even bear to listen to my beloved di Lasso, because of the reminder...″, and on another page it says, ″I have written Deng Xiaoping, who has agreed to grant to visit to A & H when he discovered that they, like him, are M."
In the front and back of the book there are a series of letters written on the spears by arranging like this
G A E M D I A L A E
R C = A R G L E D R
When you read it in a zigzag (read the first letter from top, read the first from bottom, second from top, second from bottom, etc), It says "Grace = Madrigal Leader."
The Cahill isn't there but is needed in the 39 Clues game.
The Morse Code on pages 39–65 reads: THERE IS A MADRIGAL WATCHER
To: All Janus
From: Cora Wizard
My fellow Janus,
The other branches have nothing on us—no style, no wit, no sense of how to run the world. Certainly they don't have state-of-the-art strongholds underneath the canals of Venice, Italy! But despite our best efforts, they are collecting new Clues every day—OUR Clues. There is even a rumor that the Tomas have a fresh lead on the Chinese legend.
Use your creativity. Everything we want is out there.
We just need to reach for it.