Why kill the fittest old folks? That's the first question late-blooming amateur sleuths and retirees Charlie North and Ben Tucker need to answer. Here's Question #2. Are Charlie and Ben prime targets to be killed? The answer is yes, of course. And here's Question #3. Would a Cougar be interested in a 70ish-year-old guy? It seems like a totally outrageous question when we're talking murder, but SPOILER ALERT,...