A Touch of Brimstone - S4.E21

When a group of hoaxsters called the Hellfire Club mix murder with their mischief, Steed and Emma demonstrate a few tricks of their own. The whalebone corset, high laced boots and spiked dog-collar Emma wears as the "Queen of Sin" were designed by Diana Rigg herself, and resulted in A Touch of Brimstone being banned from American TV.