At least five people wished Gavin Dordress, the playwright, dead the night of his ill-starred party. It was that night Gail Garrett and Bea Townley quarreled openly for the leading role in his new play-which no one had read. The next morning he was found shot to death, a chessman imprinted on his forehead, and nearby a letter of farewell that sounded suspiciously like one of his stage characters speaking. The police called it a suicide. But Cynthia Dordress and Lee Mappin called it murder. For weeks suspense rode high. Then a new and amazing clue sped a seemingly hopeless hunt to a thrilling finish.