The further scenes set within Tegan's mind in this episode are thoroughly compelling, are a technical masterpiece, and acted with such confidence by Jeffrey Stewart as Dukkha and, especially, Janet Fielding as Tegan. One gets the impression that this story was written with Fielding's talents in mind; it's tough to imagine her skills remaining dormant until the rehearsals for this story, nor obvious to those who were making Doctor Who until it came time to write Kinda.
Of course, it could be that Christopher Bailey's script is so meticulously well written and so superbly brought to life by director Peter Grimwade that any actor could find inspiration in the work. Richard Todd as Sanders is ideally cast as the stoic leader of the expedition, but turns in an equally strong performance after Sanders opens the Box of Jhana, leaving him with a childlike mentality. And, no, I'm not crediting Todd's performance to Matthew Waterhouse's infamous behind-the-scenes coaching of the long-time movie and TV veteran.
Although, speaking of Waterhouse, it must honestly be said that he is actually rather good in this story. In fact, ever since the Season 19 production block started, Waterhouse has shown a great improvement from his shaky start during Season 18. I actually quite enjoyed his performance in Castrovalva (broadcast before Kinda, but made directly after it), and the theme of Adric siding with the enemy is done better in Four To Doomsday that you almost believe that he's doing the same with Hindle in Kinda, until Adric lets us (but not Hindle) in on the ruse shortly afterward.
It's become a national sport to bash Adric/Matthew Waterhouse (one in the same to some people), but, apart from some admittedly poor scenes in his early days, he's nowhere near as bad or annoying as he's often made out to be. You know Kinda is a special kind of story when I'm starting to praise Matthew Waterhouse...