"The National Palace in Mexico City has played a central role in the country's rich history. It was built using materials from the ancient Aztec palace that once stood on the site. For more than 500 years, the palace has been occupied by royalty and political leaders. Today, it contains the offices of the president of Mexico, as well as those of the Federal Treasury and the National archives. While its historical significance is clear, some Cahills wonder why the Tomas have the National Palace under 24-hour surveillance. Is there something hidden inside? And does it have anything to do with the Janus Clue that went missing in Mexico years ago? Collect all the cards in this combination to unlock a Clue."