"Immortal Clay" is set at a pottery shop run by two debt-ridden brothers, Richard Marling (Paul Eddington, later seen in "Something Nasty in the Nursery"), who handles the business end, and Allen Marling (Gary Watson, from "Death on the Slipway," "Lobster Quadrille," and "Wish You Were Here"), the young genius handling production. In the last of his ten appearances (half of which are lost episodes from season one), One Ten (Douglas Muir), Steed's superior, wants to know if an unbreakable ceramic has been discovered by Allen Marling, but does not approve of Cathy Gale's frequent involvement, her being an "amateur!" A dead body is found drowned in a vat of liquid clay, and was apparently on friendly terms with Richard Marling's wife Anne (Rowena Gregory, later seen in "The White Elephant"), who complains about her husband being too busy to spend time with her. There is also the airhead blonde assistant (Didi Sullivan) in love with Allen Marling, which drives her ardent suitor Harry Miller (James Bree, later seen in "Killer") mad with jealousy. A desperate Miller decides to steal Allen's unbreakable invention and sell it to De Groot (Steve Plytas, later seen in "A Touch of Brimstone"), a foreign importer ready to make a killing on the deal. Uninteresting soap opera stuff, but that's really all there is.
