Where's Mommy? by Beverly Donofrio illustrated by Barbara McClintock*

My favorite aspect of this book is the illustrations.
Dual stories are being told with the same plot.
A mouse and a girl are friends but keep it a secret in fear of grown up reaction.
One night Maria, the girl and Mouse-Mouse, are getting ready for bed but cannot find their mothers to tell them a story.  A surprise ending!
*Highly recommend.