The story of Chappaquiddick is not only about Ted Kennedy or Mary Jo Kopechne. It was also about the Boiler Room Girls, the women who were Mary Jo's co-workers -- and her friend. Many theories about what happened that night have been explored in this podcast. And in the final episode of Cover-Up, a mysterious letter reveals new details about the story that has been shrouded in secrecy for nearly 50 years.  To continue the discussion, join our Facebook group to share your thoughts and theories or reach us directly at [email protected]. And for more on the case, go to people.com/coverup.