DON'T FORGET

Shopping for ingredients to bake her mother a birthday cake, Sarah stops at the greengrocer's for an orange and the bakery for advice but is reluctant to go to Singer's; though they have the flour and eggs she needs, she's fascinated and horrified by the blue numbers the nice old couple have tattooed on their arms. When Mrs. Singer finds out what troubles the eight-year-old (``I know how you got them,'' says Sarah. ``And that they are your secret''), she reassures her (``The numbers should never be a secret'') and, in helping her to bake the cake in her own kitchen so that it will be a surprise, recalls the first cake she made in the same pan. An appealing story that gently but effectively makes its point. Rand's cheerfully nostalgic watercolors suggest the late '40s. Recipe for orange sponge cake included; it's a good thing Sarah had adult help. (Picture book. 6-10)