Video: 'Valerie Percy Slaying Mystery 50 Years Later'

(Sunday, September 18, 1966, a few minutes after 5:05 a.m. CDT) — Valerie Jeanne Percy, the 21-year-old twin daughter of Republican Senate nominee Charles H. Percy, was beaten and stabbed to death by an intruder early this morning in her second-floor bedroom at the family’s palatial home on Lake Michigan in Kenilworth, Illinois.

Video: 'Murder In The Mansion: The Unsolved Case Of Valerie Percy'

Although her stepmother briefly saw the killer and authorities mounted an exhaustive investigation, the case remains unsolved.

In 2014, a new book on the murder would identify the late William Thoresen III, who lived with his wealthy family less than two blocks from the Percy home, as the likely suspect. Ironically, Thoresen suffered a fate similar to that of Miss Percy, murdered while lying in his bed.

Charles Percy went on to be elected as a Republican U.S. senator from Illinois on Nov. 8, 1966, serving three terms from 1967 until 1985.

He was also mentioned as a Republican presidential hopeful from 1968 through 1988.