As in ‘The Star Beast’, this represents Davies leaving behind previous showrunner Chris Chibnall’s multiverse and taking things back to basics, as the very best science fiction tends to do. After the Newton escapade, the episode is just a two-header, with the Doctor and Donna in isolation on the ship. It is reminiscent of Alien, of Silent Running, and, given (bit late to give a spoiler alert, but: spoiler alert) the fact doppelgangers of the Doctor and Donna turn up, Solaris. Of course, it’s not at all pretentious, with huge dollops of The Hitchhiker’s Guide to the Galaxy thrown in too – the way the doppelgangers can’t “get the arms right” is a giggle for the kids watching. There’s a delightful puzzle to the episode that works as a satisfying mini-movie, while also delivering some intriguing lore tidbits and tease Davies’ overall new arc.