Young Cam Jansen and the Zoo Note Mystery — David A. Adler

It's field trip day in Cam and Eric's class. Only where is Eric's permission slip? He had it on the bus, but now it's gone! Did someone take it? Did it blow away? After a few red herrings, Cam's click-click memory kicks in just in time for Eric to join the class on their field trip to the zoo.
Perfect for new readers, these Young Cam Jansen Easy-to-Read mysteries feature easy-to-follow storylines, brief sentences, and visual clues within the illustrations, and will introduce readers to feisty Cam, whose adventures can be followed in the Cam Jansen series for transitional readers.