Through a misunderstanding, Junie B. thinks that her new baby brother is really a baby monkey, and her report of this news creates excitement and trouble in her kindergarten class.

When the local library tries to cancel story time because the babies are too loud, it's up to Boss Baby and this trusty team to save the day!

From the moment he arrives, it is obvious that the new baby is boss and he gets whatever he wants, from drinks made-to-order around the clock to his executive gym.

Baby Billy, from the House of Mustache, and Baby Javier, from the House of Beard, bravely conquer their biggest foe, bedtime, until they both succumb to an enchanted book, which takes them to dreamland where they become the stuff of legend.