Stewart Inkster is a highly intelligent 13-year-old boy living with his father in Vancouver, Canada. He tells the reader that he always wanted a sister to turn their family triangle into a square. Stewart’s mother dies. She has always been the base of the triangle, and her absence leaves Stewart and his father, Leonard, bereaved. Stewart says: “For a long time he was Sad Dad twenty-four-seven, and I was Sad Stewart twenty-four-seven, and together we were Sad Squared, and it was just a big black hole of sadness” (4). Stewart’s only comfort is his cat, Schrödinger.

Leonard works as a television news producer. A year after his wife dies, he begins dating the station’s news anchor, Caroline Anderson. She is divorced and has a daughter named Ashley, who is a year older than Stewart. When the couple decides to live together, Leonard tells Stewart that they will be moving into the Anderson home. Steward isn’t sure that this is how he wants to acquire a sister.

The narration shifts to Ashley, Caroline’s 14-year-old daughter. Unlike Stewart, Ashley isn’t a gifted student. She is vain, self-absorbed, and concerned about social status. Ashley says of herself: “I am just stating a fact when I say that my friends were jealous of me and my life.