Warning: Spoilers ahead for Doctor Who season 15, episode 4, "Lucky Day."Doctor Who's new UNIT team.

Established franchise stars like Jemma Redgrave's Kate Stewart will feature heavily in the recurring Doctor Who villains during Chris Chibnall's era as the showrunner. Although details about the spinoff's plot are still sparse, Doctor Who season 15, episode 4, "Lucky Day", includes a throwaway line that gives away one of the project's locations.

Mel's Mission In Doctor Who Season 15 Must Be Connected To UNIT's Sea Devils Spinoff

Kate tells Ruby about Mel's water-based investigation in "Lucky Day"

doctor who mel scarf

During Ruby's phone conversation with Kate in "Lucky Day," Gibson's character apologizes for disturbing Kate and explains she was looking for Mel Bush (Bonnie Langford). Kate's heartwarming reply of "I've always got time for you" is quickly followed up by the reveal of why Mel isn't at her post. In short, Mel is en route to Australia after reports of "something strange happening" in Sydney Harbor. No attention is drawn to the line, but it can only really be there because of The War Between the Land and Sea and UNIT's coming clash with the Sea Devils.

"Mel's on her way to Sydney. There's something strange happening in the harbor."

- Kate to Ruby in Doctor Who season 15, episode 4, "Lucky Day."

Langford debuted as Mel during Doctor Who's classic era, serving as a companion to both Colin Baker's Sixth Doctor and staying on to travel with Sylvester McCoy's Seventh. Mel's return during the brief comeback of David Tennant as the Fourteenth Doctor in the third of three specials to celebrate Doctor Who's 60th anniversary reinstalled her among the franchise's ing cast. UNIT has since been making full use of Mel's experience of seeing the universe with the Time Lord, as proven even further by her assignment in "Lucky Day."

How The Events Of Doctor Who Season 15, Episode 3 Will Change UNIT's Spinoff

UNIT doesn't end "Lucky Day" in good shape

UNIT is faced with a new kind of threat in "Lucky Day" thanks to Conrad Clark (Jonah Hauer-King) and his movement of far-right conspiracy theorists, Think Tank. Conrad's problematic community doubts the existence of alien life and tries to spread its rhetoric of UNIT being nothing more than a front for the UK government to line its own pockets with extra tax payments while keeping everyone afraid and in line. He is, of course, incorrect. Sadly, the disinformation he spouts to his followers and the world at large does stick with portions of the population.

Kate and the others will be fighting an especially uphill battle during their encounter with the Sea Devils.

So, rather than being tasked with containing an alien threat, UNIT finds itself trying to clear its own name as a legitimate organization that strives to keep the public safe. Ultimately, it's not something UNIT is set up for, and Think Tank succeeds in tarnishing UNIT's credibility, and even leads to the possibility of the UK branch of the organization being shuttered. With more attention on the team than ever before, and with many doubting their true motivations, Kate and the others will be fighting an especially uphill battle during their encounter with the Sea Devils.

Related
Doctor Who Season 15, Episode 4 Ending & Real Meaning Explained

Ruby Sunday's return to Doctor Who for "Lucky Day" has a complex ending that's also glaringly obvious, wrapping up an unconventional episode.

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Kate may even have been removed from her position by the time of the spinoff show after failing to neutralize the unorthodox threat caused by Conrad. However, with Redgrave already confirmed to be among the cast, this could mean that Kate is acting solely out of the duty she has to the UK and her late father's legacy, and without the official of the larger UNIT organization. So, The War Between the Land and Sea has its origin within a Doctor Who episode, but it remains to be fully seen how "Lucky Day" will change things for UNIT.

Doctor Who Season 15's Release Schedule On Disney+

Episode

Title

Release Date (2025)

1

"The Robot Revolution"

April 12

2

"Lux"

April 19

3

"The Well"

April 26

4

"Lucky Day"

May 3

5

"The Story and the Engine"

May 10

6

"The Interstellar Song Contest"

May 17

7

"Wish World"

May 24

8

"The Reality War"

May 31

  • Doctor Who Season 14 Poster

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    Doctor Who
    Release Date
    December 25, 2023
    Network
    BBC
    Directors
    Douglas Camfield, David Maloney, Christopher Barry, Michael E. Briant, Barry Letts, Michael Ferguson, Richard Martin, Peter Moffatt, Pennant Roberts, Lennie Mayne, Chris Clough, Ron Jones, Paddy Russell, Paul Bernard, Michael Hayes, Timothy Combe, Morris Barry, Gerald Blake, Graeme Harper, Waris Hussein, Rodney Bennett, Mervyn Pinfield, Hugh David, John Gorrie

    WHERE TO WATCH

    Streaming

    The latest Doctor Who series introduces the Fifteenth Doctor, ed by new companion Ruby Sunday.

  • A Doctor Who Sea Devil Holding a Sword
    The War Between The Land and Sea
    Network
    BBC One
    Showrunner
    Russell T. Davies
    Directors
    Dylan Holmes Williams
    Writers
    Russell T Davies
    Franchise(s)
    Doctor Who / Whoniverse
    • Headshot Of Gugu Mbatha-Raw In The Photocall for the Netflix heist film 'Lift'
      Uncredited
    • Cast Placeholder Image
      Russell Tovey
      Kate Lethbridge Stewart
    • Cast Placeholder Image
      Jemma Redgrave
      Colonel Christofer Ibrahim
    • Cast Placeholder Image
      Alexander Devrient

    The War Between The Land and Sea is a Doctor Who spinoff series from BBC. The live-action series will focus on the iconic Sea Devil species.