"The City on the Edge of Forever" is routinely listed as the best episode of the series (Kirk and Spock travel into the past to repair damage that a deranged McCoy has done ... only to learn that this means allowing a beloved pacifist to die so that she won't prevent U.S. entry into World War II). That pacifist, Edith Keeler, was played by this then unknown actress. Identify this actress, the sister of a best-selling author, who would make a name for herself playing Alexis Carrington on the series Dynasty.
Joan Collins