I’ve lost count of how many times there has been a Doctor Who episode set on a space station or inside of a ship in peril. The set-up is always the same, The Doctor and companion(s) arrive, are almost immediately separated from the TARDIS, realize they are in danger and are met with suspicion by the survivors. There are often dark corridors and some running involved, and ultimately a puzzle is solved and a sacrifice is made.
So, this time, The Doctor has to save the day before they are all turned into space zombies or run out of oxygen. As it turns out, this isn’t such an accident after all, since oxygen is a commodity that can be sold by the breath. The Doctor sums it up with “The universe shows its true face by asking for help. We show ours by how we respond.” He, of course, responds by risking his life to save Bill, only there are unexpected consequences.
There, too is a confrontation with Nardole over The Doctor’s duty with respect to whoever is contained in the vault.