King & Kayla and the Case of the Secret Code by Dori Hillestad Butler
A lovable dog helps his human girl solve a mystery.
Kayla and Mason both got mysterious letters, written in code. What does Kayla know? –The same person left both letters. It’s someone she and Mason both know. The two letters are the same, except for the second word.What does King know? –Jillian left the letters. What do the letters say?