Late on the night of July 18, 1969, a car went off a bridge on Martha’s Vineyard. With a young senator from Massachusetts, Edward Kennedy, at the wheel, the Oldsmobile sank into the water beneath the Dike Bridge. In a sequence of events that instantly became famous, Senator Kennedy escaped from the submerged vehicle and swam to shore. By 2:30 a.m. he had made his way back to his hotel in Edgartown, where he was sighted in the lobby. He made 17 phone calls to family members and associates. But not until 10 hours after the accident did he call...