The Madman Theory

An exciting mystery by the masterly Ellery Queen Madman or murderer? That was the question and it was Police Inspector Omar Collins who had come up with the answer. All he had to go on was: the victimEarl Genneman, wealthy president of Genneman Labs; the sceneright in the middle of a busy state park; the murder weapona shotgun that was still missing; the witnessesMyron Retwig, Red Kershaw, Bob Vega, and Buck James, all friends or employees of the deceased; the motiveunknown; the suspectseveryone!