Robert Johnson was an American singer-songwriter and musician. Described by Eric Clapton as "the most important bluesman who ever lived" Johnson's shadowy and poorly documented life and death at the age of 27 has given rise to much legend and one of the best is documented below.
According to legend, as a young man living on a plantation in rural Mississippi, Robert Johnson had a tremendous desire to become a great blues musician. He was instructed to take his guitar to a crossroad at midnight. There he was met by a large black man (actually the Devil) who took the guitar and tuned it. The Devil played a few songs and then returned the guitar to Johnson, giving him mastery of the instrument. This was in effect, a deal with the Devil mirroring the legend of Faust. In exchange for his soul, Robert Johnson was able to create the blues for which he became famous.
I wouldn't know about such things but whenever I pass this spot I picture a young Johnson, guitar in hand, making a pact with the old Devil himself. You might want to come here at Midnight and report any spooky goings on or sell your soul for a life of caching?! 
The cache itself is an unusual container but should be familar to regular cachers. The clue should leave you in no doubt.
Happy caching...and pact making if that's your thing! 