The Kay Tracey Mystery Stories were written under the pen name of Frances K. Judd, published originally by Cupples & Leon. Millie began writing volumes for this series with volume #3, The Mystery of the Swaying Curtains, published in 1935. She wrote 11 books in this series, ending with volume #14, The Sacred Feather, published in 1940. She did not write #13, The Forbidden Tower,as it was written by Edna Stratemeyer.

The Kay Tracey series is similar to Nancy Drew® in that Kay is also 16, has only one parent, and has two chums that help her solve mysteries. Unusually, though, for a series book heroine, Kay's mother is alive and it is her father that is deceased. The series originally was published from 1934 to 1942. Later it was reprinted in various formats by other publishers from Garden City Books Inc. to Berkley Publishing Corporation to Bantam Skylark--in wrap style dust jacket to picture cover to paperbacks.

The original books had boards that were yellow and the dust jackets like the one pictured above, featured a yellow background, red lettering, and an open book--text on the left and a scene from the book on the right. These are harder to find, especially those books with glossy frontispieces.

The Mysteries:

• volume#1 The Secret of the Red Scarf, 1934
• volume#2 The Strange Echo, 1934
• volume#3 The Mystery of the Swaying Curtains, 1935 (Benson)
• volume#4 The Shadow on the Door, 1935 (Benson)
• volume#5 The Six Fingered Glove Mystery, 1936 (Benson)
• volume#6 The Green Cameo Mystery, 1936 (Benson)
• volume#7 The Secret at the Windmill, 1937 (Benson)
• volume#8 Beneath the Crimson Brier Bush, 1937 (Benson)
• volume#9 The Message in the Sand Dunes, 1938 (Benson)
• volume#10 The Murmuring Portrait, 1938 (Benson)
• volume#11 When the Key Turned, 1939 (Benson)
• volume#12 In the Sunken Garden, 1939 (Benson)
• volume#13 The Forbidden Tower, 1940
• volume#14 The Sacred Feather, 1940 (Benson)
• volume#15 The Lone Footprint, 1941
• volume#16 The Double Disguise, 1941
• volume#17 The Mansion of Secrets, 1942
• volume#18 The Mysterious Neighbors, 1942

Beginning in the early 1950's when the books were re-published, they were updated and the first book underwent more changes than the rest. So, if you have a book dated after 1942 on the copyright page or a later date added to a copyright page, you do not have the exact original text and may want to collect those to get a true feel for the originals.