“Oxygen” may appear to be a standalone episode; however, if my theory is correct, then this may be a major piece to set up the arc for Series 10.

The episode explores the concept of capitalism applied to colonizing space.  The Doctor, Bill, and Nardole arrive on a nearly desolate space station after receiving a distress call.  The currency on board is breaths of oxygen.  While it is abundant on planets, it is a commodity in space and the occupants are charged accordingly.  Once the crew accomplishes their mission, those back home (known only as “The Union”) deem them expendable and keeping them alive is too costly.  As the “organic components” are deactivated, the corpses’ suits join the ranks to cut costs and kill those still alive.

There seems to be an ongoing theme in this season of technology that does not value human life, which is fitting since it has been announced that we will see the return of the Mondasian Cybermen.  For those who do not know, there are two different races of Cybermen on Doctor Who: the classic Cybermen from Mondas and the reboot Cybermen built by Cybus Industries from the parallel universe known as Pete’s World.  Mondas was Earth’s twin planet, and it was knocked out of orbit long ago.  To survive, its inhabitants had to build robotic suits, and they eventually became Cybermen.

We never actually learn the crew’s planet of origin in this week’s episode, but I believe it to be Mondas.  My theory is that this incident is the lighting of the fuse that will lead to their creation, and these suits are essentially prototype Cybermen.  The Doctor says that shortly after this, there is a rebellion that ends capitalism in space, but then they make a completely new mistake.  The Cybermen in classic Doctor Who served as a metaphor for the looming threat of the Soviet Union (They are cold, grey, and want everyone else to think like them.), and the collapse of interstellar capitalism could lead to a cosmic Marxist revolution.