Dr Who 10.0 Oxygen

Nardole accompanies the Doctor and Bill to a space station to answer a distress call. Most of the crew have been killed by their smartsuits, robotic spacesuits capable of independent movement which are the only source of oxygen on the station, forcing the TARDIS crew to don spares.

It’s good to be back in space. There is a good first act as we establish what’s happened (Zombies in Space). Then in the final act, in a single scene the Doctor appears to solve everything and _snap_ he is back at university. What just happened ?