Young Cam Jansen and the knock knock mystery

Eric's Grandma Minnie and Grandpa Max keep hearing someone knock at their door, night and day, but find no one there, so Cam tries to solve the mystery using her amazing memory.

Bibliographic Details
Main Author: Adler, David A.
Format: BOOK
Published: Penguin Young Readers, an imprint of Penguin Group USA 2014
Series:Penguin young readers. Level 3, transitional reader