Millie is eleven (going on twelve) and enjoys doing what kids usually like to do: riding her bike and dreaming of the day she can convince her family to get a dog. She also writes in her diary daily. But instead of writing to herself, she writes to her twin brother Billy, who died before he was born. Alright, so it’s not totally normal, but it’s manageable. Millie’s life as she knows it comes to a screeching halt, however, when her parents decide to separate. Her mother gets a new boyfriend, and her father moves into a new place - an apartment - with a big sign on the door that says NO DOGS ALLOWED. As she struggles to get her parents back together - not just for her sake, but for the sake of her future dog as well - Millie is elated when her father moves back in a short while later. She can’t understand why her parents aren’t happy at the reconciliation until she learns the truth: her father has moved back in because he has been diagnosed with cancer.