Molly Greene has always loved mustard. That is, until her (former) best friend Olivia Anderson tells the entire fourth grade that Molly has been infected with a bad case of the deadly Mustard Flu. And anyone who plays with Molly is in danger of catching it Now Molly finds herself deserted by almost all the other kids in her class. And her only chance at getting her old life back is to find a cure for the Mustard Flu. Before it kills every single one of her friendships.