Combine raisins and rum in a small saucepan. Bring to a boil; cover, remove from heat, and let stand 1 hour.
Preheat oven to 450°.
Unfold piecrust in a 9-inch pie plate. Fold edges under and flute.
Combine eggs, egg whites, and next 3 ingredients in a medium bowl. Stir in raisin mixture. Pour mixture over crust. Sprinkle with nutmeg.
Bake at 450° for 10 minutes. Reduce oven temperature to 325°. Bake 25 minutes or until set. Chill until ready to serve.