Inferno has been magical up until now.
The Doctor's back on Earth having escaped the parallel universe, but he's unconscious. Stahlman is pushing ahead with penetration zero, clearly affected, but the Doctor isn't on hand. A semi conscious Doctor babbles about output pipe 2 and tells Liz to reverse the systems. Liz dashes to the control room and orders it. The Doctor explains to Liz and the Brig where he's been, the Primords arrive before penetration zero.....
When the Doctor explains to Liz and the Brig what happened in the parallel worlds it was brilliantly delivered, he's such a great actor.
In truth I think episode 6 was the peak, but part 7 is another great episode.
Watching Inferno, I've been reminded of 1984 drama threads, the bleakness of it, but the story is very similar to Conan Doyle's When the world screamed.
I was so gutted that this was the last appearance of Liz, she was a fantastic companion, and featured in some superb episodes. The series was intelligent, she was cutting, the format worked so well. I love Katy Manning, so much, but Jo Grant was not a patch on Liz, the series seemed to go backwards after Inferno, so many dull and repetitive stories would follow.
The series has been outstanding, and Inferno has been its peak, fantastic overall.