Harriet is a girl who absolutely loves costumes. She wears them everywhere she goes! Whether she is visiting the dentist, shopping at the local supermarket, or getting ready for her super special dress up birthday party, Harriet is always in character. Her two dads have decorated their home perfectly for her big day, and Harriet has chosen her absolute favorite outfit. But they quickly realize they forgot one very important thing for the party. They need party hats! Dressed in her special penguin errand running costume, Harriet sets off into the city to find the perfect hats. Instead, she stumbles right into a flock of actual penguins and gets completely carried away! Now she is headed straight for the freezing arctic. Follow along to see if Harriet can navigate her way back home to her dads before the party starts.