Mrs. Eleanor Marlowe is young widow who works at Purrington Street Library with her fellow cats and lives in an apartment by herself — not counting the extended family of mice who secretly live with her. But harboring mice is a serious offence in Cat City. Neighbors wonder why Mrs. Marlowe never invites anyone over for catnip tea, and the mice wonder if she's fattening them up for the kill. When officers from the Department of Catland Security show up, can Mrs. Marlowe outwit the police and save her mice?