This is one of Margery Sharp's shamelessly affectionate stories but at any rate a new one for her old audience about an elderly woman who is given charge of a youngster, Antoinette, during and after World War II when her ""pretty mummy"" is in America. Antoinette is an untamable, unteachable little creature who turns out to be hopelessly retarded -- vermin and tureen are the only two words that she learns in all this time and she likes to play tiddlywinks with rabbit droppings (touches such as this make it possible to cut the sweetness with a garden shears). But pretty mummy comes back and is going to take Antoinette away when she shows signs of regressing from a little animal to a vegetable and. . . . Miss Sharp resolves it in a fortuitous fashion which enables her innocents to prevail. Yesterday's Bundle for Britain, today's CARE packaged sentimentality, but it would indeed be folly to underestimate the giver or the takers.