As in ’The Star Beast’, this represents Davies abandoning earlier showrunner Chris Chibnall’s multiverse and taking issues again to fundamentals, as the easiest science fiction tends to do. After the Newton escapade, the episode is only a two-header, with the Physician and Donna in isolation on the ship. It’s paying homage to Alien, of Silent Operating, and, given (bit late to present a spoiler alert, however: spoiler alert) the very fact doppelgangers of the Physician and Donna flip up, Solaris. In fact, it’s by no means pretentious, with enormous dollops of The Hitchhiker’s Information to the Galaxy thrown in too – the best way the doppelgangers can’t “get the arms proper” is a giggle for the youngsters watching. There’s a pleasant puzzle to the episode that works as a satisfying mini-movie, whereas additionally delivering some intriguing lore tidbits and tease Davies’ total new arc.