Mary Jo Kopechne had been dead for several months when her parents began to have serious questions about what really happened the night of July 18, 1969. At first, Gwen and Joe Kopechne had believed Senator Ted Kennedy’s account of that evening. “They trusted him,” says Mary Jo’s aunt, Georgetta Potoski, 75. “They loved the Kennedys. But later on, they started to question what happened.” Ted Kennedy could never escape the unanswered questions about his 10-hour delay in reporting the accident to Edgartown police. “The longer it went on, more and more inconsistencies were discovered and he wasn’t telling Gwen...