The 39 Clues Wiki
The 39 Clues Wiki

Additional Books!!!

The Black Book of Buried Secrets is a bonus book in The 39 Clues series released on October 26, 2010. It was written by Mallory Kass and contains an introduction by Rick Riordan.


This book is the ultimate source of Cahill knowledge. It contains every secret, every Cahill weapon and gadget, all the strongholds, and each agent and founder. In this book, you will discover the true story of Madeleine Cahill as well as what happened after Isabel Kabra was charged with murder. Nothing has been held back. Seven Cahill Agents came together to bring you this book, betraying their branches and their most deeply held beliefs. They did it because there is an enemy approaching, far more powerful than the Cahills.

Keep this black book close at all times. Be ready. Be watching. THE ENEMY IS AT THE GATE.


For the past five hundred years, the Cahills have been silently changing the world. Their desperate hunt for the 39 Clues lies behind some of history’s biggest enigmas—the curse of the Hope diamond, the race to summit Mt. Everest, the wild life and death of Harry Houdini. And now—finally—the secrets are out. With an introduction by Rick Riordan, The 39 Clues: The Black Book of Buried Secrets reveals the shocking truth about history’s most notorious family, including:


Beware of Spoilers!

  1. Morse Code (page before Introduction): NEVER FORGET THE MOROCCO ATTACK
  2. Madeleine's Portrait (page 24) – 12/4 is 3, so A = 3: FIND THE SAFE DEPOSIT BOX
  4. AGENT UPDATE: Amy and Dan Cahill (page 39) – A=Z, B=A, C=B, etc. KEEP GIDEON'S GOLD RING SAFE
  5. Founder Archives: Winston Churchill (page 58): A DEAD LUCIAN DUKE IS STRONGER THAN A LIVE TOMAS KING
  6. AGENT UPDATE: Ian Kabra (pg. 72) – ignore letters R, A, X, N, Y, E, S, Z: DOOMSDAY
  7. Flag Code (page 86) – key on Page Before Introduction: THE KIDNAPPING PLOT
  8. Spy Penny (page 86; same picture on Card 176: Spy Penny): WE SEE ALL
  9. Page 102 – first letter of every word: NELLIE IS A TARGET
  10. Founder Archives: Annie Oakley (page 129): PROTECT THE SERUM AT ANY COST
  11. JONAH'S JOURNEYS: ANTARCTIC EDITION (pg. 154; same picture on Card 147: Antarctic Bling ) – Small words in the CREDITS section: JONAH KNOWS WHERE IT IS
  12. Founder Archives: Raoul Lufbery (pg. 165) – "Offset13" means move 13 letters backwards: CLUE MOVED FOR SAFEKEEPING
  13. Page 173 – Key in clock at end of book: DAN IS A TARGET
  14. Ekaterina Crest (page 187): DANGER! DANGER!

15.Page 173 possible heist times 12:00