Grace had shown [Amy] a hand-drawn map of Africa and told her stories about the adventures she'd had when she was a young explorer. (3.9)
The clue hunt is an inheritance of a different kind. Instead of money, it allows Grace to pass on her knowledge and experience of the world to her heirs. Of course, we're not sure they've realized it yet. They seem in it more for the power.
Could the treasure be a lost Egyptian tomb.... or pirates' gold? (3.43)
Amy's imagination goes wild early on in the clue hunt, wondering where the adventure around the world will take her. She probably gets these ideas from all those books she's always reading.
[Amy] couldn't help being curious. She loved mysteries. (3.44)
Amy's curiosity is a big asset on the hunt. Her love for mysteries and puzzles comes in handy during all the library research they have to do, which is a task that Dan finds tedious, like most other eleven year old boys.
"[Grace] was a cartographer. A map maker and an explorer. She made that globe herself." (4.70)
As far-reaching as the Cahill clan is, we're under the impression that Grace might have changed the world in her own ways as she explored it. Have Amy and Dan changed anything during their exploration of the globe?
As [Dan] pressed the last letter, the whole shelf swung outward. (4.101)
You can't have a good treasure hunt without a secret passage. Preferably one inside a bookcase. At least this one wasn't opened by pulling a lever disguised as a book—like every other secret passage bookcase ever.
"This is just the kind of mystery Mom would've loved!" (6.17)
The hunt isn't just about a trip around the world for Amy and Dan, it also lets them explore their family history and find connections to their parents that they didn't know they had. Could that maybe be what Grace had in mind when she designed the hunt?
Amy wasn't shy around them at all. She loved librarians. (8.72)
Amy's scared of a lot of things, but she feels at home in a library. To her, a library is a safe place; it's a place where she can have all sorts of adventures without actually going out into the world. She can explore without, you know, exploring.
"We have to explore the Catacombs." (15.39)
This trip isn't all about sunny locales and fancy French foods. Amy and Dan encounter some pretty scary and dangerous things as they explore the world. History has some dark secrets.
"Stop, mortals," Nellie translated. "This is the empire of death." (16.6)
Okay, so Grace's clue hunt is a little more dangerous than The Amazing Race. The fact that she's sending an 11- and a 14-year-old into these locations makes us wonder if she hadn't gone a little mental before her death.
"We have to hurry and get to Vienna." (19.92)
At the end of the book, we get a clue as to where Amy and Dan will head next. Where else do you think the hunt will take them?