With codewords and secret signals perfected, best friends Rachel and Joon are ready to spend their summer practicing spycraft--especially if they can uncover secrets like the one Joon's parents have been keeping, that his family is about to move out of town.

When eavesdropping leads them to a ring rumored to have belonged to Anna "Nancy" Smith Strong--according to local Long Island legend, the only female member of George Washington's famed Culper Spy Ring--they think they've hit the jackpot. Then they discover Nancy left a coded message in the ring!

Decoding her message leads to another cryptic clue, and then another, and soon Rachel and Joon are racing to decipher a series of puzzles that must surely lead to hidden treasure! But can they solve the final mystery before Joon's moving day? And just what did the centuries-old spy hide away--and why?

Sarah Beth Durst's skillful blend of Revolutionary War history and suspenseful contemporary storytelling will keep readers guessing to the last satisfying page.