The ""silent friends"" -- French animated dolls -- are no more mechanical than Nina Martin and friend Muffin, two Manhattan mystery-solvers. Twelve-year-old Nina spends part of every summer day in her father's 3rd Avenue antique store where she plays with the two dolls (one writes several phrases and the other draws pictures) which are not actually for sale. Within a few days time, two men, each giving his name as George Ballantine III, wish to purchase the dolls. After a few fruitless efforts, Nina and friend are busily working their way to a conclusion; it is the dolls who supply the clues, and Nina who finally discovers their exact meaning. There is a lot of standard monkey business before a long lost fortune is uncovered in the form of a platinum cage.