In a saucepan over medium heat, bring the cranberry juice to a boil. Remove from heat, add gelatin and stir until dissolved.
In a mixing bowl, beat the cranberry sauce for 1 minute. Add gelatin mixture and stir until well mixed. Chill in refrigerator for 2 1/2 hours or until thickened, but not set.
Remove from fridge and fold in whipped topping until mixture in thoroughly blended. Spoon into pie shell and chill until firm.