Have you ever wondered where lost things go when you lose them, and how they magically seem to reappear in a place you already looked? This story revolves around Rosemary and Finn, two brownie siblings living within a colony of brownies in the walls of an apartment building. Rosemary works as a finder of lost human items and sets them up to be returned to their human owners. It's an essential job as it helps keep the brownies a secret from the residents in the apartment building. But fed up with her job only finding socks, and with the encouragement of her brother Finn, she asks for a promotion. This leads to the siblings having to work together to find a lost stuffed dog for a little girl who lives in the building. But they must do this without being seen by the humans in the building. Tensions rise between the siblings as Rosemary and Finn learn why their job is so important, not only to the colony but to the humans who they share the building with.