How can a TV show that's been on the air for more than 54 years suddenly come up with a pilot episode? Season 10 of "Doctor Who" does exactly that, taking flight with a debut that harks back to the very first 1960s episode.

The premiere of the forthcoming tenth season, to be shown on 15 April, is called "The Pilot". Named for an alien pilot in the story, the title is a joke by showrunner Steven Moffat about the industry convention of referring to a new show's very first outing as a "pilot" episode. Moffat wanted the show to be accessible to new viewers as well as confirmed fans, so he wrote the season 10 opener as a primer to the format of the show -- a new pilot episode, if you will.

But in typical Moffat style, there are extra layers to the joke. "The Pilot" evokes the actual first episode of "Doctor Who" ever made, "An Unearthly Child", broadcast all those years ago on 23 November 1963. That 1960s adventure saw a pair of curious teachers encounter a mysterious schoolgirl and her grandfather, who turned out to be time travellers. Moffat's 2017 update inverts that storyline, involving a curious student who encounters a mysterious teacher.

The curious student is Bill, played by TV newcomer Pearl Mackie, and the mysterious teacher is none other than the Doctor, played by Peter Capaldi.

Capaldi's wandering Time Lord has apparently settled down to teaching classes in a university in Bristol, but he hasn't entirely given up a life of intrigue. The arrival of Bill and her star-crossed crush Heather brings entirely new complications for the Tardis crew...

Pearl Mackie breezes into the show with cheerful self-assurance, playing Bill as an instantly likeable new companion brimming with smart questions. It's nice to have a companion who's seen a few sci-fi movies (on Netflix, of course). She has an instant rapport with Capaldi, rounded out by a touch of comic relief from Matt Lucas as returning sidekick Nardole.

Season 10 is the last for both lead actor Capaldi and showrunner Moffat, but there's no trace of maudlin self-reflection in "The Pilot". It's a pacy, lighthearted and (mostly) self-contained little story that deftly reiterates the core format of the show while firmly establishing the chemistry between the Doctor and Bill (and Nardole).

There's only the merest hint at strands for the forthcoming season, which will see the Tardis crew threatened by monsters and villains old and new in adventures across time and space, including a revelation Moffat says will "melt your brains".

"Doctor Who" returns on 15 April on BBC1 in the UK and BBC America in the US. You can also check out a double bill of the first episode with the premiere episode of "Who" spin-off "Class", featuring a cameo from Peter Capaldi, in US movie theatres on 16 and 17 April.

Correction, 1:48 p.m. PT: This story initially misspelled the last name of the showrunner for "Doctor Who." He is Steven Moffat.

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