Middle follows the story of a spunky little girl who is uneasy about welcoming another sibling into the world. Her Mother, Father, and her Big all seem to be rather happy with this news, but the unknown of this newest addition makes her unamused. After careful consideration, she starts to grow warmer welcoming another baby into their corner. When the day arrives and the new baby is here, she starts to worry and grow with fear. The two titles, Big and Little have already been claimed. What will be her new title name?