"It's an orchid!" she exclaimed.  "A white one - see, Moms - on a red heart - who could have sent me an orchid?"  Excitedly she took the little card out of the envelope and read:

Dear Schoolgirl Shamus:
Is this you first orchid?
I hope so.  See you tonight.
Jim

Trixie blushed to the roots of her sandy hair.  "Did you ever have an orchid in your life?" she asked her mother.  "A beautiful white orchid  from - of course you've had them from Daddy - but from a boy?

The Mysterious Code
(p. 169)

Title :
Trixie Belden and the Mysterious Code

Author :
Kathryn Kenny
Ghost writer believed to be Nicolete Meredith Stack

First Published :
1961

Chapter Titles :
1.  No More Bob-Whites?
2.  Trixie's Big Idea
3.  "The Winnah!"
4.  Treasures in the Attic
5.  The Acrobatic Alphabet
6.  A Musical Mystery 
7.  Thieves!
8.  Foreign Intrigue
9.  Lost in a Blizzard
10. A Caller in the Night
11. The Mask Comes Off
12. "This Can't Be Me!"
13. Going Partying
14. At the Police Station
15. The Most Fun Ever
16. The Show Takes Shape
17. Brom's Surprise
18. Night Watch

Setting :
Sleepyside, New York.

Synopsis :
Acts of vandalism force the board of Sleepyside High to crack down on secret clubs, and the Bobwhites are forced to prove their worth by holding an Antique show to raise money for UNICEF.  Preparation for the show uncovers some truly valuable antiques and attracts some unwanted attention, putting the life of Bobby and Trixie in danger. 

Characters : 
Trixie Belden
Jim Frayne - newly adopted son of the Wheeler's
Honey Wheeler - Trixie's best friend
Brian Belden - Trixie's eldest brother
Mart Belden - Trixie's "almost twin" brother
Diana Lynch - the newest Bob-White
Mrs Belden - Trixie's mother
Peter Belden - Trixie's father
Bobby Belden - Trixie's six year old brother
Miss Trask - Honey's governess
Celia Delanoy - the Wheeler's Maid
Regan - the Wheeler's Groom
Tom Delanoy - the Wheeler's chauffeur
Madeleine Wheeler - Honey's mother
Mrs Lynch - Diana's mother
Tad Webster - classmate of the Bob-White's
Spider Webster - Police Officer, Tad's oldest brother and friend to the Bob-Whites
Sergeant Molinson - head of the Sleepyside Police Force
Mrs Vanderpoel - A friendly Dutch woman who has been a long-time friend of the Belden's
Brom Vanderheidenbeck - A whiskered, old man who lives in a small cottage in the Wheeler's game preserve.
Oto and Kasyo Hakaito - Japanese brother's who have a fresh produce shop in the village and are interested in Samurai swords.
Mrs. Bruger - the Lynch cleaning woman
Mike - the counterhand at Wimpy's Diner

Villains :
Bull Thompson - a young boy who shovelled Mrs Vanderpoel's paths and later stole the desk from Bobby and Trixie.
Snipe Thompson - Bull's uncle, who broke into the clubhouse, stole the swords and later held Trixie at gunpoint while he and accomplice attempted to steal the antiques.

Points of Interest:
This was the first book written by a new author, and published three years after the last Campbell book, and there were a few signs of inconsistency.

The author must have paid little heed to Jim's background history as this is where the biggest inconsistencies occur.  Trixie finds a jewellery box that had belonged to Jim's Aunt Nell that was hidden by the daughters of the previous owner, Mrs Spencer when they were young.  Jim tells Trixie that his mother told him Jonesy, his step-father, was accused by his aunt and uncle of stealing the music box and even his mother thought so.  This introduces two problems.  Jim was ten when his father died and his mother married Jonesy sometime after.   In The Secret of the Mansion, Jim tells Trixie and Honey that after Aunt Nell died, his mother never heard from his uncle again (p. 48) and it does not seem that Jim ever met his Uncle.  It doesn't appear that Jonesy ever met the Frayne's and, therefore, could not have stolen the music box.  Also, Mrs Spencer mentions that her daughter, who now lives in Canada, is currently visiting and confesses that she and her sister hid the music box.  If Jonesy, was on the scene it must have been less than five years ago and her daughters could not have possibly grown up so quickly and the Manor House would not have been empty for "so many years" as Trixie states in The Secret of the Mansion (p. 37).

Molinson, who seems to be a contemporary of Spider's in The Mysterious Visitor, becomes a Sergeant in this book and has a well-established dislike for Trixie and her involvement in mysteries.

The book is set either in late January/early February as Di holds a pre-Valentine's Day party.

Trixie's birthday is May 1 (p.161).

This book is probably most remembered for the orchid Jim sent Trixie, addressing her as "Schoolgirl Shamus" and the author telling the reader that Jim had recently noticed "that Trixie was a pretty girl" (p. 122).