Doctor Who: Every Modern Companion's DEFINITIVE Episode

Considering that Yaz is one of the longest serving companions of the revival, it's hard to nail down a definitive episode for her. Demons of the Punjab was an option, but upon closer inspection, the story doesn't actually give Yaz much to do. Likewise, Can You Hear Me provides some great development for Yaz but not much in the way of focus. Ultimately, I've gone for the slightly outside choice of Eve of the Daleks. 

This is the episode that finally confirms (far too late) what had gone unspoken for a very long time - that Yaz has romantic feelings for the Doctor. The scene where Yaz finally admits this to herself and Dan is amongst her best moments, but it's not what stands out to me the most. Because this is also the episode in which Yaz starts to really challenge the Doctor on her behaviour, becoming frustrated about being sidelined for her 'own protection', and disregarded emotionally because Thirteen is too afraid of having a mature conversation and would sooner pretend she hasn't noticed the way Yaz feels. There's tension in this episode between the duo, which is finally allowed to surface and bring them all the closer for it, as Dan quietly plays Cupid in the background (when is he not in the background? Bless him). 

The episode itself is a bit of a banger, and whilst it's not quite Heaven Sent, the episode does make very good use of its time-loop gimmick to apply emotional strain on the characters, exacerbating their honesty with each other. Yaz isn't the hero of the story but her persistence and determination is showcased throughout - she's given more to do than normal and is an integral part of the team. There are certainly episodes where Yaz 'does more', but I think this one still takes the 'quintessential' title as this is where Yaz's emotional arc hits its apex. Shame the next episode spends more time on silly pirate jokes than actually following up this solid setup. 'Thasmin' could have been a big, era-defining step forward for Doctor Who, but sadly the show seems to stop just shy of properly exploring that possibility. In this episode, at least, we get scraps of it.