Prince William and Kate Middleton show off spy-themed activities with their children.

[They have just moved into their new home, Adelaide Cottage in Windsor, and on Thursday, Prince George, Princess Charlotte, and Prince Louis will all be enrolled at the Rum Rook School. And as if that wasn't enough, the three Cambridge children, along with their parents Prince William and Kate Middleton, are apparently participating in spy-themed activities.

Yes, according to PEOPLE, the Duke and Duchess of Cambridge wrote the foreword to a children's book titled Puzzles for Spies, written by officials at the Government Communications Headquarters, and according to PEOPLE, the British intelligence, security, and cyber agency is paying the book's advance and royalties to the Royal Foundation of the Duke and Duchess of Cambridge to support the charity's mental health initiatives.

"We are delighted that the brilliant minds at GCHQ are busy working on their third puzzle book and that this edition is designed for young readers," William and Kate write in the foreword. 'As a family, we are no strangers to the important work of GCHQ. We continue to be impressed by the way our staff constantly confront new threats and how dedicated they are to protecting our national security."

"We are also very proud to be a part of the GCHQ team.

The couple touched on the severe impact COVID-19 has on mental health and thanked readers for supporting the Royal Foundation's mental health efforts by purchasing the book. They also shared that with the help of their three children, they will be reading "Puzzles for Spies."

"We look forward to helping the children solve the puzzles and hope that the book will bring friends and family together to start rich conversations," they wrote.

"Talking openly about mental health is the first step in removing prejudice, fear, and isolation, and bringing different perspectives together, as GCHQ has done, is often the key to unlocking solutions that we cannot find on our own."

Puzzles for Spies will be released on September 22 and will include "everything from cryptography and brain puzzles to word riddles and language puzzles," according to a release surrounding the book's debut.