Season 1, Episode 4: ‘73 Yards’

Let’s get the easy bit out of the way. “73 Yards” is not just the best episode of the season so far, but also the strongest story “Doctor Who” has produced in years — despite the Doctor (Ncuti Gatwa) hardly featuring.

That’s not to say the decade-spanning story’s success depends on Gatwa’s absence. Yes, Episode 4 gives Millie Gibson space to break out of her companion role for the first time, and she gives a nuanced performance well beyond her 19 years.

But it’s Russell T Davies’s ambitious, unpredictable script that will ensure a place for “73 Yards” in the Whoniverse history books. The episode constantly wrong-foots viewers, plays with folk stories and horror tropes, and finds a genuinely terrifying villain in a nuclear-warmongering politician.

“We are in Wales. Spectacular!” shouts the Doctor as the TARDIS materializes on a craggy cliff face. For international viewers, it’s a swift introduction to a nation that has long been associated with “Doctor Who”: Davies is Welsh, and the show is a former BBC Wales production.

In a seemingly throwaway comment, the Doctor mentions a future prime minister, a Welshman named Roger ap Gwilliam, who will lead Britain to “the brink of nuclear war” in the 2040s. “Sorry, spoilers,” he says, shooting Ruby a smile.

Adventures in the here and now are put on pause when the Doctor accidentally steps on a witchy-looking web of threads and stones, known as a fairy circle, on the grass. Ruby reads the note attached — “Rest in peace Mad Jack” — but when she looks up, the Doctor has vanished, the TARDIS locked behind him.

Ruby initially assumes it’s a prank. The strange woman (Hilary Hobson) with fluttering gray hair who’s waving her arms in the near distance? She must be in on it, too. Ruby marches off toward the nearest village, yet when she looks back, the woman is always close behind, in the style of the 2015 horror movie “It Follows.”

A friendly hiker passes by, confirming to Ruby that she, too, can see the mysterious woman. “I haven’t met you before, have I?” Ruby asks the walker. She has: The actor, Susan Twist, has had a small role in all of Gibson’s episodes to date, previously as a tea lady, a spaceship officer and a robotic ambulance. This echoes the “Bad Wolf” arc from Davies’s first season in 2005, and it’s clear that the showrunner wants us to notice Twist’s repeated presence — but why?

At Ruby’s request, the hiker goes to speak to the distant woman, and is soon running away from Ruby. Feeling uneasy but short on options, Ruby treks to a nearby pub. She never sees the woman move, but the gray-haired figure is never far behind.

One of the locals from the pub also tries to speak to the woman, and similarly sprints away in panic. Ruby leaves Wales, but the woman follows her back to London, always keeping 73 yards away, and turns Ruby’s mom, Carla (Michelle Greenidge), against her, too. “Even your real mother didn’t want you,” Carla tells Ruby. As it has at points of peril in previous episodes, snow falls outside their apartment.

A year later, Ruby meets with Kate Lethbridge-Stewart (Jemma Redgrave) from the United Intelligence Taskforce, or UNIT, Britain’s supersecret extraterrestrial task force that was first mentioned on “Doctor Who” in 1968. Kate was introduced during Matt Smith’s tenure in 2012, as the daughter of the Doctor’s old friend the Brigadier, first played by Nicholas Courtney in the early “Doctor Who” years. The UNIT team also tries — and fails — to take on the mysterious woman.

Abandoned again, Ruby accepts her fate. Gibson’s performance so far has been rooted in pain, but now a look of blank resignation clouds her eyes.

Ruby’s life cycles forward: mid-20s, 30s, 40s. During a breakup in a bar, Ruby sees a populist politician (Aneurin Barnard) on TV: Roger ap Gwilliam, the Welsh politician the Doctor warned her about.

The calmly confident Roger instantly evokes an all-time great “Doctor Who” villain. In the 2007 episode “The Sound of Drums,” the Doctor’s longstanding enemy the Master took on the form of a man named Harold Saxon (John Simm) and charmed his way into becoming prime minister, only to use his platform for destruction. Roger isn’t the Master (as far as we know, at least), but the newer character is every bit as charismatic and sinister.

“I was a jack-of-all-trades. Mad Jack, they used to call me,” Roger says. Now, it’s Ruby’s time to save the world.

Ruby joins Roger’s campaign team, and watches him become elected prime minister, promising a “bigger, bolder Britain.” For a big political rally, the team congregates at the empty Cardiff City soccer stadium (the enormous venue is another flex of the show’s newly bolstered budget). There, Ruby learns Roger’s plan: to buy Pakistan’s nuclear arsenal and declare Britain independent of NATO.

She strides across the pristine pitch toward the politician, stopping 73 yards from him. Her mysterious follower is now standing beside him, and starts talking to him. Like the hiker, Carla and the UNIT team before him, Roger runs off shouting and immediately resigns, with his deputy going on to promise “a more lenient and listening government.”

Time skips forward another 40 years, and Ruby (now played by Amanda Walker) dozes off at her high-tech care home. She wakes to find the woman there — not 73 yards away, but at the end of the bed. It starts playing out like a horror movie: The lights flicker as the woman gets closer, the shrieking score muddling with Ruby’s audibly slowing heart rate and the screaming beep of her hospital monitor. Ruby reaches out her arms, and the scene changes.

“We are in Wales. Spectacular!” In front of the older Ruby, the Doctor and young Ruby step out of the TARDIS on the Welsh coast, all those years ago. Everything becomes clear: The older woman following Ruby was herself all along, offering a warning from the future about Roger’s plans for nuclear destruction. In the season so far, Ruby’s origins have been a question mark, and this alternative future deepens the mystery.

When the two women are in each other’s presence this time around, things are different. Young Ruby notices the woman and hears her whispered call of “don’t step.” She stops the Doctor from breaking the fairy circle, and they leave the note about Mad Jack unread. The pair skip off in search of adventure, business as usual.

There haven’t been many “Doctor Who” episodes in which the Doctor’s companion drives the story. But this latest offering — arriving halfway through the season — proves what’s possible when the show’s creators not only prioritize bold storytelling, but also refuse to hold the viewer’s hand. Let’s hope they can keep it up.