Sumac Lottery is the fifth of seven kids in her (VERY) large, (EXTREMELY) unruly family. With four parents, a parrot, a dog, a rat and two cats, the sprawling Victorian house they call Camelottery is already quite full (in the best sense). But then one day, Sumac gets the news that one of their grandfathers will be coming to live with them. And not just any grandfather—a long-dormant one who fell out with his son so long ago that he hasn't been part of any of their lives.

Suddenly, everything changes. Sumac has to give up her room to make the newcomer feel at home. She tries to be nice, but the prickly old man clearly disapproves of how the Lotterys live: whole grains and strange vegetables, odd pets, a multicultural household. . . . He's worse than just tough to get along with—Grumps has got to go! But can Sumac help him find a home where he belongs?