While the Doctor plans a holiday to Metebelis Three, Jo and the Brigadier are intrigued by a mysterious death at a coal mine in Llanfairfach, which is being blamed on local company Global Chemicals.
Quest roles:
John Scott Martin(Kriz), Nicholas Courtney(Brig. Lethbridge-Stewart), Terry Walsh(Crew Member (uncredited)), Talfryn Thomas(Dave), Jerome Willis(Stevens), Stewart Bevan(Clifford Jones), Tony Adams(Elgin), Ben Howard(Hinks), Mostyn Evans(High Priest), Roy Evans(Miner), Ray Handy(Milkman), Mitzi McKenzie(Nancy)