There is the whole world, and in it, there's a city, and in that city, there's a house, and in that house, there are two half-houses, and in one of those half-houses, there lives a pair of sisters named Stella and Marigold. Stella, who's seven, likes cats and axolotls and second grade. But most of all, she likes Marigold. Marigold, who's four, likes gibbons and red paint and the plumber. But most of all, she likes Stella.

Stella and Marigold do all the regular things—like going to school, playing with their friends, sometimes going to the zoo, and sometimes getting sick—but even the most regular things have a secret side. There's a secret that involves a blanket.

And another one about wolves, a terrible storm, and two brave children. That's a very exciting secret, and no one knows about it except Stella and Marigold. And—if you read this book—you!