A little girl's anxieties about her mother's return when she's left for a few hours with her wise, empathetic ``Aunt Whistle'' are obliquely expressed in her concern for her dog Dooley when he disappears after a rabbit: ``What if he doesn't come back?...Suppose he gets lost? Suppose he forgets about us and never comes back at all!'' Aunt Whistle assures the young narrator that ``If need be, I can whistle up Dooley''; and after they finish picking apples, she does. So why not whistle up Mama? Because she'll ``come back all by herself.'' A nicely understated exploration of a common fear, as reassuring as the hugs this child gets, at all the right times, from both mother and aunt. Cannon's wonderfully expressive paintings, in bold swatches of richly saturated colors delineated with broad lines of subtler tones, capture the girl's mood and her essential security. Nice. (Picture book. 4-7)