Simple, audacious, exhilarating, with excellent lead performances.

Steven Moffat, and Doctor Who, are back.

SPOILERS

Warning: thisDoctor Whoreview contains spoilers.

Millie Gibson in a red jacket on a war-torn planet in Doctor Who episode “Boom”

Its all fun and games until someone steps on a mine.

There has certainly been peril in Ruby Sundaysfirst few adventures with the Doctor.

But even the darkest moments have occurred in the context of fairly light-hearted romps.

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These darker, more stressful episodes must tread a fine line.

More on which later.

What if that moment were stretched out into a whole episode?

Though thats not to say that the episode is entirely unfamiliar territory.

The Anglican Marines return, having first been introduced early in Matt Smiths tenure.

After that, the episode is a relentless ratcheting up of tension.

First, the Doctors life is in danger.

Then its the Doctor and Rubys lives.

Then theres a child in danger too.

Then its the whole planet.

There are too many electrifying moments to list, but Gatwas vicious delivery of Seriously?

Now you need proof,faith gyal?

is a highlight, as is his wordless, guttural cry of anguish when Canto shoots Ruby.

Oh, and Im a lot more explosive than I look and honey?

I know how I look.

This is threatening to become a list, so lets move on.

Its beautifully played by both, Ruby quietly resolute, the Doctor barely keeping a lid on his emotions.

Even though theyve not been travelling together that long, the emotions feel genuine and completely earned.

A lot of this comes down to Sethu herself, who gives a great performance.

Admittedly there are some aspects that dont fully come off.

Does that mean were on the brink of a big reveal?

It certainly feels like this particular narrative bomb has been primed for a while.

It might well be time for it to go off…

Doctor Who series 14 continues next week with 73 Yards, on BBC One, iPlayer and Disney+