Behind the Iron Mask is a musical based on a peculiar history. In 1669, in bizarre and mysterious circumstances, an unknown man was secretly masked and imprisoned for life by Louis XIV of France. He died in 1703, having been in four different jails, but in the custody of Monsieur St Mars the same jailer. The Prisoner was allowed the best of everything and given anything he desired other than human companionship; but he was not allowed to discuss his identity or the reason for his imprisonment. St Mars was sworn to secrecy in fear of death. Due to the indiscretion of the Jailer, a Gypsy becomes entrapped in the relationship between the two men.