[s3e16] — The Gammy Files

: By matching the details from the "Gammy" files to Betty’s current behavior and background, K.C. eventually confirms that Betty is indeed the enemy agent Margaret.

: K.C. discovers a photo from an unsolved case from 1977 involving a spy known as "The Gammy" .

If you are referring to a different "paper" plot, you may be thinking of Assignment: Get That Assignment! from Season 1, where Marisa writes a based on K.C.'s spy missions and they have to retrieve it before it blows K.C.'s cover. The Gammy Files | K.C. Undercover Wiki | Fandom