What's the best day of the year? A birthday, of course! Stella Batts is turning nine, and she has big plans. Her family will be going to Pennsylvania to celebrate. That's where Stella's best friend Willa moved to, and Stella hasn't seen Willa for months. It's hard not to see your best friend for that long, so this is an important trip. But before Stella can get on the plane—DISASTER STRIKES! Now instead of a birthday weekend sleepover with Willa in Pennsylvania, Stella is stuck in a hospital room in her hometown of Somers, California, with a broken leg, doctors, nurses, and a roommate who is a stranger. What's the worst day of the year? You guessed it. Stella's birthday.