1. Inferno
Episode: Season 7, episode 4
Companions: Liz Shaw, The Brigadier Not just the best episode of the Third Doctor's tenure but one of the best in the whole of Doctor Who, Inferno is an incredible piece of television. Detailing the Doctor's attempts to try and stop a drilling project destroying the Earth along with some primordal monsters, the episode does something the series never does again in the classic series it goes sideways into a parallel universe. The middle 5 episodes set there are some of the greatest the show has ever made. The location of the story is a big fact to its success. The constant moaning of the drill means characters always have to shout giving an air of fear from the very beginning while the giant industrial complex outside just looks magnificent. The parallel Earth setting is also a simply brilliant idea. and the beginning of episode 3 where the Doctor discovers the fascist world he's now trapped in (accompanied with a fantastic action sequence making full use of the stuntmen of HAVOC) sets the scene up perfectly. The characters are superb throughout the terrified but helpful Greg, the stubborn Professor Stahlman as well as Platoon 'Under Leader' Benton are all great but the parallel universe counterparts to the Doctor's best friends steal the show. 'Brigade Leader' Lethbridge-Stewart-complete with eye patch sees Courtney at his very best. He plays the character as a ruthless, dictatorial bully, but at the end his true cowardice is brilliantly and shockingly exposed. To see such great characterization in a supporting character is the mark of quality for any show, and it shows section leader Shaw (complete with miniskirt and kinky knee high boots, naturally) was Carrie John's favorite role to play she's great at being evil but switches to normal Liz brilliantly due to the sheer terror of events around her. If Doctor Who has a a greatest single episode in the classic run, it's probably part 6 of Inferno. Knowing the parallel Earth is about to be destroyed, the Doctor realizes he must return to our world to save it and must enlist the help of those who he knows he can't take back. It's an incredibly shocking moment and the whole scene within the small bunker is the most tense in Doctor Who's history, no doubt helped by some astonishingly good work from Pertwee, The cliffhanger of the unstoppable lava rolling in is the best the show ever produces, as it gives us a rare moment where we realise the Doctor's lost, and there's some people he just can't save. It's truly haunting, and sticks with you.