Preheat oven to 375 degrees. In a bowl, combine flour, brown sugar and shortening. With fingertips, rub these ingredients together until the shortening resembles small beans. Set aside.

In another bowl, dissolve the baking soda in the boiling water. Add the corn syrup and molasses; stir to blend. Pour filling into the shell and sprinkle the crumb mixture over the top.

Bake in the middle of the oven for 10 minutes. Reduce the heat to 350 degrees and bake for 25 minutes more. The filling should be set, but still quiver when the pan is tapped. Do not over bake.