Add enough water to reserved cherry syrup to make 2 cups liquid.
Heat 1 cup of the liquid to boiling and pour over the gelatin.
Stir until dissolved.
Stir in remaining liquid.
Chill until mixture is slightly thickened, stirring occasionally.
Stir in the sour cream.
Halve the cherries and stir into gelatin mixture.
Turn into a 1 1/2 quart mold and chill until firm.