On a four-mile rural road eerily nicknamed the Devil's Promenade, just off the old Route 66 in the north-east corner of Oklahoma, a paranormal mystery has puzzled spirit seekers for more than 100 years. The Hornet Spook Light – a mysterious, basketball-sized glowing orb named for the former town of Hornet – has been appearing in the night sky here since 1881. No-one knows what this peculiar, smouldering ball of light signifies, where it comes from or what it's composed of. Even the Army Corps of Engineers have concluded that it's a "mysterious light of unknown origin". It moves, spinning...