You might get the impression from watching this that the budgets were already a bit stretched for this season, so they just resorted to some green body paint to create a race of rudimentary "Swampies" who are rebelling against some human interlopers who have plonked a drilling rig off their coast. The "Doctor" (Tom Baker) and "Romana" (Lalla Ward) are still continuing their search for the Key to Tver mais...