Eleven-year-old Otto wants a dog, and his older sister Lexi wants a cat, so their mother suggests that whoever can raise enough money to pay for their pet can choose--and so the competition begins.

Eleven-year-old Otto wants a dog, but his twelve-year-old perfect sister, Lexi, wants a cat. Their mother, who works very long hours as a nurse, wants neither. Pets are expensive, so who's going to pay for everything?