The kids spend most of the book undercover and therefore much of what they say and do is, at its root, deceptive. This is always in the name of fighting evil and feels ‘necessary’. This could lead to some great discussion with your children.
In a short scene, a Zodiac signs is used to give a clue. There are also a few mentions of luck.
This book does a good job of staying ‘light’ when dealing with perilous situations. One example that steps outside of this, and is out of character with the rest of the book, comes when one character is swimming at night, mistakenly believes she sees a shark and wonders if “it would be the shark’s bite that killed her or if instead she would be snatched away, deep down, to drown in bloody darkness”.