followng up on CK's point above, and mine a bit previously:
http://www.smithsonianmag.si.edu/smithsonian/issues01/jan01/spirit.html: when people relied on sources such as torches, hearth fires and candles for illumination, night assumed a different character in the human imagination. The hours of fear descended every night, when one could easily lose one's life by falling into ditches, ponds or rivers, or being thrown by horses unfamiliar with dark paths. Demons, witches and night hags, it was widely believed, held sway in those hours. Ruffians and robbers could wreak their havoc