[5] Amy, Dan, and Nellie arrive in Vienna, where they discover Mozart had a sister, Nannerl.

Amy finds the complete sheet music from Paris online and plays it in the hotel lobby.

A woman informs them it is a song titled "The Place Where I Was Born", and Amy realizes they need to be in Salzburg.

In them, Nannerl says that she thinks Wolfgang was going crazy, as he was buying large quantities of expensive Japanese steel and going into major debt.

They also find two notes written by Grace, the first of which refers to the French word "gateau", though Amy doesn't fully understand it.

As Ian is playing the music, Amy realizes that the second message meant that the D5 key is rigged.

Because the keyboard is still intact, Amy finishes the song, revealing a hidden passage where two katanas are visible.

Amy realizes that the first message from Grace meant to take the letters "g", "a", and "e" from the word "gateau", leaving them with "t" and "u", the old chemical symbol for tungsten.

Clue Found: Tungsten (wolfram) Next Location: Tokyo Kidsreads.com reviewed the book, claiming that a reader may find inspiration in their own life and that "Gordon Korman...has done an amazing job.