Having successfully vanquished the Maestro (for now), the Doctor and Ruby Sunday find themselves on a war-ravaged planet, and the stakes are high as soon as they step outside of the TARDIS.  The Doctor must find a way to save everyone without moving an inch.

"Boom" sees the return of former Doctor Who showrunner Steven Moffat, who wrote the script.  It's an interesting break in approach from the first two episodes of this season.  The planet looks bleak, and the tension is higher than usual, with frequent tight close-ups on the Doctor and Ruby.  There's also a touch of claustrophobia, which we haven't seen to this point.

The story also features much quieter performances from Ncuti Gatwa and Millie Gibson, because the Doctor must stay as calm as possible, in order to avoid setting off the land mine underneath him.  Both actors are up for the job, as they manage to achieve an intense, but low-volume, state.  It's striking how The Doctor and Ruby have managed to feel like real chums so early into their partnership.  (Ruby wastes no time putting herself on the line at one point for the Time Lord.  It feels like an authentic response, even though they still barely know each other.)

"Boom" offers the chance for the audience to see multiple sides of the 15th Doctor.  There's been a lot of high-octane joy so far (along with occasional flashes of sadness.)  However, the sorrow is stronger than usual, and the anger also comes out more than we've seen to this point.  This Doctor isn't afraid to show his emotions, whatever they may be at the time, and it helps to flesh the 15th incarnation a little more. 

Steven Moffat has plenty to say here about capitalism, war, and religion.  The Doctor's scornful speech about all of these topics would make #12 proud.  (Did anyone ever give an angry speech better than the 12th Doctor?  Sorry, we digress.)  You can particularly feel the Doctor's contempt over the utterance of the empty "thoughts and prayers" phrase from those who cause the harm in the first place. 

There's a love interest subplot which feels rushed.  We don't have enough time to really connect to these characters to feel the full impact of the tragedy that befalls them.

Steven Moffat has a difficult job as the writer, because you know the Doctor and Ruby won't die in the end.  (Sorry if that's a spoiler.)  However, Moffat still does a good job of ratcheting up the anxiety, as the countdown to the land mine's fail-safe explosion gets closer to zero.  What's most interesting about the resolution is that it leans into the Doctor identifying as a father.  That's particularly noteworthy, given his mentioning granddaughter Susan last week.  Will this eventually tie into the story of Ruby's background?

Speaking of the mysterious companion, we have magical snow again.

"Boom" is the most traditional Doctor Who episode of the season so far.  There's still some singing, which is fine with us, and there's another appearance from the mysterious Susan Twist.  However, it's generally a straight-forward tale of suspense.  The episode flies by, and if anything, it could have used another 45 minutes to maximize the tension.

It was fun to have Steven Moffat back for a moment.  We look forward to seeing what he has in mind for this year's Christmas special.

In the meantime, we'll meet you back here next week!

The Doctor has to think carefully before his next step.  (pic via facebook.com)