Book 3 gives an insight into Big Daddy and Big Momma's family. A few days after Mr. Mouse finds a new home in Book 2 in the basement of the big old brown brick house, Big Daddy and Big Momma began making plans for their family reunion. No one was aware that a tiny mouse was hiding in the basement of the house, and tiny mouse, Mr. Mouse, was not aware of what was going on in the big old brown brick house. Book 3 gives an insight to the activities and actions of the people and the little mouse living together in the big old brown brick house.