What sets Nightmare of Eden apart from other stories of the era is the total adult nature of the plot and what lies at the heart of it: narcotic drug abuse and trafficking. Still a kid's show at heart, no one is ever seen taking the drug of choice in this story, Vraxoin (although Rigg's drink is spiked by someone surreptitiously dumping a small amount of the powder in). And how could you? Any such action would be instantly imitated by the kids on Monday morning.
Still, the effects of the drug are shown. Secker begins the story in the full throes of the drug, and is apathetic to anything and everything around him, only becoming agitated when his high starts to dissipate. Rigg goes completely off the deep end once his spiked drink kicks in, appearing as drunk as a production assistant in the BBC canteen at about 9:30 on a Friday night. Even someone being drunk and/or stoned on a Doctor Who episode is pushing the mark a bit, and it's to Nightmare of Eden's credit that the production chose to be this daring.
Another good episode. I must admit - it feels good to have the memories of one's youth validated!