Many of the world's most spectacular railways were constructed during history's most turbulent periods and are now associated with some of mankind's ugliest deeds. A vast number of the stories surrounding these railroads have been lost to the passing years and are now unknown, even to those that work or travel on them every day. This documentary series unearths the most captivating tales behind these railways and offers viewers a glimpse into their hidden and, often, a very dark and chilling past.