Sister has been an only child for 4 years now. She has had her parents' undivided attention at any time of the day, or night. Her parents have been planning a new addition to their little family for some time now. Sister's parents thought they had prepared her for the upcoming "bundle of joy". Sister thought she was excited about the new baby's arrival; until the day came. Confused and feeling alone, big sister's mind starts wandering. Her imagination is in overdrive with situations that seem logical to a 4-year-old. Sister's home was filled with such joy and laughter. Now the house is filled with bottles and diapers from the baby. The stress of having a new baby in the home is making big sister unsettled and feelings of confusion start to set in.

A 4-year-old's overactive imagination can become something quite magical during playtime. But this wasn't playtime, and the sister starts imagining situations that leave her scared. She begins to feel alone. When she sees all the attention going to the baby, the big sister develops feelings of jealousy. She just wants things to go back to normal, and for mommy and daddy to not be so tired anymore.

Big sister overhears her mom and the doctor talking about her "mysterious" illness. This sets forth the motion of big sisters' adventure with a new baby in the house. Big sister understands that her problems came when the baby arrived. She is trying to problem solve this by herself instead of talking to her parents. She can't understand how someone so little can cause so many issues

Even with her new brother causing disruption in her house; she secretly likes him. He and his weird smell are starting to grow on her. Big sister starts to understand that she isn't the only child anymore, and that mom and dad still love her. Being a big sister comes with responsibilities. Big sister has a change of heart and begins to see the baby as her parents do. With love and adoration, the way they still look at her.