The first full-length novel by Ellen Klages.

It is [[UsefulNotes/WorldWarII 1943]] and eleven year old[[note]] (well, ten at first, but she turns eleven after a month of in-story time)[[/note]] Duodecima "Dewey" Marie Kerrigan is on her way to Los Alamos, New Mexico, to meet her father. When she gets there, she learns that Los Alamos doesn't officially exist and that she is not to call anyone "doctor" because people might get suspicious. This is nothing new to her, of course. There have been lots of secrets since the war started, but now there are more than ever, most of them having to do with "The Gadget", a mysterious weapon that the adults are working on and that people say will help them win the war. It's only at the end that Dewey realizes just how big everything is.

This novel has a sequel, ''White Sands, Red Menace''.
!!Contains contains examples of:
* BlindWithoutEm: Dewey. Becomes a problem when she breaks her glasses in the sequel.
* CypherLanguage: With Greek of all things.
* EmbarrassingMiddleName
* EmbarrassingFirstName: Duodecima.
* FreeRangeKids: All the kids in the story are allowed pretty much free reign. This was the norm for the time, however.
* HugeSchoolGirl: Suze, who is as tall as most of the boys in her class.
* IJustWantToHaveFriends
* TheMasquerade: Duh.
* MissingMom: Dewey's mother left when she was a baby; it's not until the sequel that we meet her.
* NumericalThemeNaming: Dewey's birthday is December 12. Twelve-twelve. Her father is obsessed with math. Hence her name (Duodecima), which is the Latin word for twelve.
* OddFriendship: [[spoiler:Dewey and Suze.]]
* OpenSecret: The testing of "The Gadget".
* OnlyKnownByTheirNickname: You would want to be too if your name was Duodecima.
* PinkySwear
* PresentTenseNarrative: A couple of the Dewey eccentric chapters. Is done rather well.
* SecretWeapon: Though not a secret to the reader.
* ThisIsMySide: Suze towards Dewey while the later [[spoiler:is staying with her family because her father has gone to Washington D.C.]]
* {{Tomboy}}: Suze again.