Preheat the oven to 325 degrees. Prepare the graham cracker crust in a springform pan. Refrigerate the pan until needed. Melt the chocolate over low heat. Add the rum. Set aside. Beat the cream cheese until fluffy. Gradually beat in the sugar, sour cream and vanilla. Beat in the eggs, one at a time. Mix well. Place the bowl over HOT(!) water and stir until smooth. Pour one quarter of the batter into another bowl. Set aside. Mix the chocolate into the remaining batter. Stir over HOT(!) water until smooth. Take the springform pan from the refrigerator. Pour in the chocolate batter. Gently pour the plain batter over the top of the chocolate batter. Form swirls in the batter with a fork (some of the chocolate should show). Bake for 50 minutes. Cool to room temperature. Remove the rim from the springform pan. Refrigerate overnight. Serve.