>> yes, my name is ruth kennedy and i'm calling from nashville, tennessee, i was on the phone with my daughter and she screamed and said oh, no and the phone's gone dead. and is there anything you can to do, can you go check? >> oh, no. those two words play back again and again in ruth's worried brain. and so began a mystery. and a story too unbelievable for some of its most intimate participants. what happened to caroller kennedy? >> coming up. that question, would take years to answer. >> not just what happened to carol, but who was behind it. >> she didn't have any enemies? >> none, none. >> we were just stunned. >> we were just stunned. >> when "dateline" continues. that covers heartworm disease, ticks and fleas, round and hookworms. dogs get triple protection in just one simparica trio! this drug class has been associated with neurologic adverse reactions, including seizures. use with caution in dogs with a history of these disorders. protect him with all your heart. simparica trio. when it comes to laundry, everyone thinks their way is the right way. protect him with all your he