(SPOILER ALERT) On the 39 clues, after you collect the clue copper, you learn that Hope Cahill hid this clue in a microchip and hid that on the right side of her left wrist, concealing the clue in her left arm.
Amy Cahill hid a clue in her arm in "The 39 Clues" series. She had a small microchip implanted under her skin which contained a vital clue to the location of the 39 Clues treasure.
Nellie Gomez hid a clue in her arm, specifically in the form of a microchip that contained information needed by the Cahill family in "The 39 Clues" book series.
Tomas.
On the 39 clues, in the My Cards section and the My Clues section, you learn that the Tomas branch of the Cahill family hid the clue cocoa in the mountains of Machu Picchu, Peru.
The X-Ray clue. Hidden in Hope Cahill's arm is a micro chip. It uncovers Honey.
Budapest
morroco
she was Anne Cahill. she changed her name and address to prevent other branches from discovering her existence, as they thought she died when the ship sank. she was carrying a clue with her.
James Cahill Is Not A Lucian
the Tomas
Grace is Amy's and Dan's beloved Grandmother who took care of them over the weekends. She dies in the beginning of book 1. She was like no other grandmother, she still had some spunk and was a wild as her grandchildren. In her will, she let a handful of Cahill's deiced if they want a million dollars or one clue.
RESOLUTION: fine print to guess seek out Richard S