Mainly ranging from unsolved, cold, controversial, critical, disputed, or unexplained crimes and criminal cases; wanted fugitives who are at large; missing individuals; and paranormal occurrences.
The series was then acquired by CBS in 1997, adding actress Virginia Madsen (as a co-host alongside Stack, announcing special alerts, bulletins and updates), where it continued for a short run of 2 seasons.
The series ran re-runs of NBC, CBS, and Lifetime episodes in syndication for a number of years until it was resurrected by Spike TV (Now known as the Paramount Network) in 2008.
(A spin-off special court show, series titled "Final Appeal: From The Files of Unsolved Mysteries", which had cases of accused criminals claiming their innocence, is not inherently considered part of the main Unsolved Mysteries broadcast history, however, these episodes were all later shown as episodes in the Spike TV version of the show.)
Also note that FilmRise in 2019, released/published on YouTube and Amazon Prime, digitally enhanced NBC, CBS, Lifetime and Spike TV, episodes on streaming.