"The Buddy Files: The Case of the Lost Boy," by Dori Hillestad Butler (Whitman, Albert & Company, ages 6-8)
This first book of this lovable series launches Buddy, the golden retriever, as an astute canine detective. Buddy (once known as King) is separated from his beloved family. He's determined to find them, but before he can, he's adopted by Conor, a heartbroken boy in a need of a friend. When Conor disappears, Buddy draws on everything he knows to find him.