Dori Hillestad Butler

After their shocking discoveries on Summer Island, Marly, Sai, and Isla have one final set of clues to follow before reaching the end of their search.

"Marly, Sai, and Isla are back on the hunt. After finding Mr. Summerling's hidden treehouse, they've discovered a new set of clues for them to follow, leading them straight to the heart of their mysterious neighbor's life: his house. The same house Marly has been living next to all of these years, which, they discover, is filled with hidden rooms and staircases. With just a few scraps of papers as clues, and Mr. Summerling's angry son on their tails,...

Through a series of letters, Simon, a grumpy and jealous cat, and good-natured Baxter, his boy's dog, discuss the upcoming parade in which Baxter will participate for the first time.

While searching for his mysteriously lost human family, Buddy the dog is adopted by another family and helps solve the mystery of their missing boy.

When a series of strange ghostly happenings disrupts Seattle Public Library's Halloween party, it's up to Kaz, Claire, and Little John to go underneath the city and investigate.

Trying to communicate with his human owner (and detective partner) can be frustrating for King the golden retriever as he uncovers clues in a missing dog case.

When King's favorite blue ball goes missing, he and Kayla must put together clues to figure out where it went.

When a mysterious letter written in code arrives at King's house for his human, Kayla, he follows the trail of the person who left it.

Kaz are Claire are on the case again—this time, they're looking for Kaz's long-lost uncle! Their search takes them to a bakery and a movie theater. Along the way, they meet another kid ghost detective. Will Kaz and Claire be able to figure out what's going on?

Now that Kaz can finally pass through walls without feeling all "skizzy," he can go explore Beckett's secret room at the back of the library. What he finds there is a mystery he never expected!