"Spyfall" is the two-part premiere of the twelfth series of the British science fiction television programme Doctor Who, first broadcast on BBC One on 1 and 5 January 2020.
In the episodes, the Thirteenth Doctor (Jodie Whittaker) and her companions Graham O'Brien (Bradley Walsh), Ryan Sinclair (Tosin Cole), and Yasmin Khan (Mandip Gill) are enlisted by MI6 to investigate a former agent and an alien threat.
While Yaz and Ryan investigate Barton (whose DNA they discover to be 93% human), who invites them to his birthday party the following day, Graham and the Doctor find O in the Australian outback.
Ada takes her to the residence of polymath Charles Babbage, where the Doctor summons a Kasaavin via a figurine identical to the one in Barton's office, hoping to return to the 21st century.
Ada suddenly grabs the Doctor's hand as she fades and they accidentally travel to Paris during World War II instead.
They are rescued by British spy Noor Inayat Khan, though the Master continues to pursue them, posing as a Nazi officer through the use of a perception filter.
The Doctor meets with the Master atop the Eiffel Tower, where the latter reveals that he had the Kasaavins kill spies in order to get the former's attention and claims that Gallifrey has been destroyed.
With help from Ada and Noor, the Doctor destroys the Master's filter and turns the Nazis on him while her group uses his TARDIS to return to the present.
Speaking at a conference, Barton reveals that the Kasaavins will rewrite humanity's DNA to utilise its storage capacity as hard drives.
The Master, forced to live through the 20th century without his TARDIS, arrives in time to see the figurine device activate, only for it to fail after the Doctor planted a virus in it in the past.
After setting up the means for her companions to survive the plane crash, the Doctor returns Ada and Noor to their respective time periods and wipes herself from their memories.
She also visits Gallifrey's ruins to confirm the Master's claim, where she discovers a recording of him confessing to destroying their home planet after realising their understanding of Time Lord history was a lie based on the "Timeless Child."
[7][8] Bradley Walsh, Tosin Cole and Mandip Gill also reprise their roles as Graham O'Brien, Ryan Sinclair and Yasmin Khan, respectively.
The website's critical consensus reads, "A fresh suit, new faces, and some exciting espionage are fun enough, but the Spyfall, Part 1's final moments inspire hope for an absolutely epic new season of Doctor Who.