Sometime in the 9th Century, three armies defeat a powerful enemy and hack its body in three pieces to be hidden away at the Ends of the Earth. But the holder of the last piece is killed before he can bury it. Archaeologists Lin (Charlotte Rich) and Mitch (Nikesh Patel) discover it in Sheffield on New Years Day, 2019. They accidentally bring it back to life and it summons the other fragments. The Doctor (Jodie Whittaker) and her companions Graham (Bradley Walsh), Ryan (Tosin Cole), and Yasmin (Mandip Gill) are traveling through time watching New Years Day celebrations from various time periods and run into the two archaeologists. Lin speaks of a kind of squid on the wall but the Doctor finds only slime because the creature has attached itself to Lin’s back, taking control of her mind and body.
At Ryan and Graham’s home, they find that Ryan’s absentee father Aaron (Daniel Adegboyega) has returned to make amends with his son. Graham is sceptical but supports Ryan trying to know his grandfather. The Doctor and Yasmin search for the creature, which has forced Lin to steal a police-car and uniform. Analyzing the slime tells the Doctor that they are searching for a scout Dalek. It brings Lin to an archive base, kills its guard, and uses his fingerprints to access the archive. It steals a Dalek ray gun from the collection, travels to a warehouse, and kills the owner, then constructs a Dalek casing out of scrap metal. The Doctor and company find Lin freed of Dalek control, but the Dalek has entered a government communications headquarters, massacred the staff, and is trying to summon a Dalek fleet.
Unable to contact UNIT because it is mothballed for bureaucratic reasons, The Doctor and crew, Aaron and the archaeologists, all go to the headquarters and destroy the signal, damaging the Dalek’s casing in the process, but the mutant inside possesses Aaron and threatens to kill him unless the Doctor takes it to the Dalek home planet Skaro. The Doctor takes it to a supernova instead and Ryan saves Aaron at the last moment as the Dalek falls into the supernova. Back home, Aaron declines to travel in the TARDIS and they leave.
The episode was written by showrunner Chris Chibnall and directed by Wayne Yip. It was a New Years Day Special instead of a Christmas Special, the only episode aired in 2019. There were no opening titles. It received 95% on Rotten Tomatoes. SF fans recognized similarities to the novel The Puppet Masters (1951) by Robert A. Heinlein, the films Invaders from Mars (1953), Jack Finney’s novel Body Snatchers (1954), films The Brain Eaters (1958), Operation Annihilate (1967), and The Puppet Masters (1994). Nicholas Briggs, an old friend to Doctor fans, was the voice of the Dalek. We finally got a glimpse of the stern resolution of the Doctor inside Jodie Whittaker’s goofy wonder, but some critics were not impressed by the plot. I thought it was the most powerful and exciting episode yet from this Doctor. There were a couple of great laughs.