Episode is loosely based on the Taman Shud case, a real life mystery in Somerton, Australia. A man with no tags in his clothes was found dead propped up against a tree. His suitcase was found in a railway locker. The only thing found in his pocket was a line of poetry. The identity of the man was never discovered.
The Return of Persephone poem was written by Alec Derwent Hope circa 1955.