Doctor Who ending explained: why did Jodie Whittaker turn into David Tennant – what was the Master’s plan?

Jodie Whittaker’s final Doctor Who episode, The Power of the Doctor, aired last night. It was, characteristic of a Chris Chibnall script, an episode with a lot of moving parts, which raised more than a few questions. What was the Master actually up to? Why did Yaz leave the Doctor at the end? Why did Jodie Whittaker regenerate into David Tennant at the end?

Here’s everything you need to know about The Power of the Doctor.

What was the Master’s Dalek Plan?

As ever, it’s quite an… let’s say it was quite an elaborate plan from the Master, with multiple layers to his latest attempt to trap/kill/humiliate/flirt with the Doctor.

In 2022, the Master kidnapped fifteen seismologists, both to get the Doctor’s attention and to stop the seismologists from alerting anyone to what the Daleks were doing to volcanos. When captured, the Master released some Cybermen to occupy UNIT, and then escaped back to the early 1900s, where he started pretending to be Rasputin. This was presumably the plan for a while, because at the same time the Master kidnapped the seismologists, he also defaced famous paintings so that they depicted him-as-Rasputin.

From 1916, living as Rasputin, the Master put the second phase of his plan into action. With the help of the Cybermen and a kidnapped alien, the Master constructed a tenth planet in Earth’s solar system; this planet, which could convert organic matter into cybernetic matter, was intended to act as a power source for the Master’s new body-swapping device. With the body swapping device, the Master was going to steal the Doctor’s remaining regenerations, and then impersonate her as he spread destruction across the galaxy (starting with Earth and the Dalek/volcano attack and the Cybermen/UNIT attack).

Did that make sense? Barely, probably. Really, it was all about the Ra Ra Rasputin sequence, everything else is secondary. (Not just the plan, the past sixty years.)

Who were the older Doctors? And what was the deal with Jo Martin?

After the Master hijacks the Doctor’s body and forces a regeneration, the Thirteenth Doctor appears at a crossroads on the edge of a cliff. It’s a representation of her subconscious, where she meets representations of her former selves – this is the first time we’ve ever seen something like that in the show itself, though similar concepts have been explored before in books like Timewyrm: Revelation. (You don’t need to seek that out though, don’t worry.)

Peter Davison, Colin Baker, Sylvester McCoy, and Paul McGann each appeared as manifestations of the Doctor’s fifth through eighth incarnations. (Fun fact: Paul McGann, who starred as the Doctor for one night only in 1996, has only appeared as the Doctor in regeneration episodes.) David Bradley, who previously played the first Doctor in Peter Capaldi’s final episode, also appears to represent William Hartnell.

Davison and McCoy also shared scenes with their former companions Tegan (Janet Fielding) and Ace (Sophie Aldred). These Doctors were holographic representations of Whittaker’s Thirteenth Doctor, but they appeared as the Fifth and Seventh Doctor to Tegan and Ace because those are the Doctor’s they had an emotional connection with.

A hologram of Jo Martin’s Doctor also appears, helping Yaz to defeat the Master and the Cybermen. Martin is a new-old Doctor, introduced in Series 12 as a representation of the Doctor’s distant and unknowable past; her brief cameo here is explained as an attempt to fool the Master.

Why did Yaz leave the Doctor?

When it becomes clear that the Doctor is going to regenerate, there’s clearly an unspoken understanding between Yaz and the Doctor that this would be the end of their time together. Maybe it’s something they’d discussed before; maybe they just know each other well enough to know that neither would want to continue their almost-relationship if the Doctor became someone new. In a sense, it’s like that line from The Curse of the Fatal Death. “I’m sorry Doctor, but you’re just not the woman I fell in love with anymore.”

Charitably, it’s a sad yet understated departure for one of Doctor Who’s longest running companions, an exit that at the very least saw her find new friends; less charitably, it’s an abdication on Chris Chibnall’s part, and can only be read as the Thirteenth Doctor treating Yaz worse than the Tenth ever did Martha. You decide!

Who were the former companions at the end?

The episode ends with Graham (Bradley Walsh) setting up a support group for former companions of the Doctor – a way for them all to keep in touch and share stories from their travels, finding friendship with the only other people who would understand their unique experiences.

You’ll have recognised, of course, Graham, Yaz, and Dan, each of whom were companions of the Thirteenth Doctor. (Ryan presumably is still in Patagonia at this point, with actor Tosin Cole having been busy filming in America during the production of this episode.) They’re joined by Kate Stewart – daughter of Alistair Gordon Lethbridge-Stewart, who appeared alongside five Classic era Doctors – as well as Ace and Tegan, all three of whom returned earlier in The Power of the Doctor.

There were also a number of new faces at the end of the episode. Jo Jones (Katy Manning) was a companion to the Third Doctor, and appeared alongside Matt Smith’s Eleventh Doctor in The Sarah Jane Adventures, while Mel Bush (Bonnie Langford) travelled with both Colin Baker’s Sixth Doctor and Sylvester McCoy’s Seventh Doctor in the 1980s. They were also joined by Ian Chesterton (William Russell), the very first Doctor Who companion in 1963, a science teacher kidnapped by the First Doctor. (Things were different then.)

Why did the Doctor regenerate?

After all of that back and forth with the Master, and the lengths Yaz and friends went to to save and restore the Doctor, she was still hit by a stray laser beam. It was, in the end, a random and almost meaningless regeneration – which is quite nice, in its own way.

Why did the Doctor become David Tennant again?

Who knows! It’s clear that, when Doctor Who returns for its 60^th anniversary specials next year, we’ll have a story about why exactly Jodie Whittaker regenerated (degenerated?) into David Tennant rather than Ncuti Gatwa, but for now we can only speculate.

For the moment, at least, it seems likely that Neil Patrick Harris’ character may have had something to do with this unusual regeneration, though we don’t yet know who Harris is playing. (There’s a lot of speculation he might be playing the Celestial Toymaker, a villain from the 1960s – a villain also sometimes known as the Crystal Guardian, which might be apt for a Diamond Anniversary story – who briefly changed the Doctor’s appearance over the course of their confrontation.)

If you’ve got any more questions about Doctor Who you’d like to make sense of, do send a tweet or an email.