On July 18, 1969, Ted Kennedy attended a party on Chappaquiddick, a small island adjoining Martha's Vineyard and connected to it via a ferry. The party was a reunion for a group of six women, known as the "boiler-room girls", who had served in his brother Robert's 1968 presidential campaign. Also present were Joseph Gargan (Ted Kennedy's cousin), Paul Markham (a school friend of Gargan's who would become United States Attorney for Massachusetts under the patronage of the Kennedys), Charles Tretter (an attorney), and John Crimmins (Ted Kennedy's part-time driver). Kennedy was also competing in the Edgartown Yacht Club Regatta,...