Wash and pick over cranberries. Place in a medium saucepan with water, and sugar. Bring to a boil, reduce heat, stir and simmer for 10 minutes or until cranberries burst.
Slightly mash the cranberries with the back of a wooden spoon to insure all skins are broken. Add the cinnamon, nutmeg and allspice. Mix well.
Remove from heat and mix in the blueberries (don't be afraid to break a few, but don't over mash either). The sauce will thicken as it cools.
Transfer to a bowl, cool slightly and place plastic wrap directly on top of sauce to cover. Refrigerate until chilled.
