To prepare the biscuits, combine flour, sugar, baking powder and salt in a large bowl. Cut in shortening with a pastry cutter or two knives until mixture resembles coarse meal. Add buttermilk; stir just until moist.
Preheat oven to 375 degrees F.
To prepare the fruit filling, combine cherries, plums, sugar, cornstarch, nutmeg and orange juice. Mix gently. Spoon into a 9-inch square or 1 1/2-quart baking dish.
Drop biscuit dough over filling to form 9 mounds. Bake 45 minutes or until biscuits are golden and filling is bubbly.