The episode stars Jodie Whittaker as the Thirteenth Doctor, Mandip Gill as Yasmin Khan, and John Bishop as new companion Dan Lewis.
En route, the Doctor experiences a psychic vision of Swarm, a mysterious being, escaping from its millennia-long imprisonment by the Division.
In present day Liverpool, Dan Lewis arranges a date with museum worker Diane before attending a shift at the soup kitchen and heading home.
The Doctor and Yaz arrive after Dan's abduction, investigating his house and discovering what appears to be a Lupari invasion fleet approaching Earth.
Karvanista reveals that the Lupari are in fact saving humanity from Earth’s imminent destruction by the Flux, an unknown entity that defies all laws of space and time and consumes everything in its path.
[7] Guest actors within the episode include Annabel Scholey, Rochenda Sandall, Sam Spruell, Craige Els, Steve Oram, Nadia Albina, and Jonathan Watson.
[9] Filming was originally set to begin in September 2020,[10] but eventually commenced in November 2020 due to the COVID-19 pandemic's impact on television.
[19] An "extended cut" of the episode aired on BBC America later that day featuring an additional two minutes of content that had been edited out of the initial broadcast to allow for television advertisements.
The site's consensus reads, "Setting a crowded table for this season of Doctor Who, 'The Halloween Apocalypse' is an ambitious opener that should leave fans feeling optimistic.