From the introduction:
A state Senator, Ambrose Gray, gets stabbed to death in his own home. His son, Representative Richard Gray, is the prime suspect, found at the scene red-handed. His daughter, who has a few secrets of her own, recommends a good private eye. The family gardener, Michael Grief, doesn't seem immediately involved, but he just might have a better motive than anybody else.
Shades of Gray is a one-shot scenario for the game A Dirty World.