10 Doctor Who Problems That Time Travel Would Have Solved
4. Bill's Long Wait
Did The Doctor just not like Bill or something? While they seemed to make a great pair, her sudden assault and technical murder seems to be enough to make The Doctor forget he's standing in front of a Time Machine.
Bill is taken down to the lower decks of the ship they have arrived on. It is parked on the edge of a black hole, messing with the flow of time so that it is much slower for The Doctor, Missy and Nardole but much quicker for Bill. While they dither, she waits ten years.
The Doctor elects to take the elevator down to find her. The elevator. The TARDIS can travel anywhere in time and space and...anyway, once he arrives, he discovers that he is just too late. Bill has been converted into a Cyberman, one of the original Mondasian Cybermen that had last made their appearance in the 1966 serial The Tenth Planet.
The ending is shocking, sad and sudden, only slightly overpowered by the return of John Sim's Master as well. Yet it could all have been changed had The Doctor simply hopped in the TARDIS, nipped downstairs and brought her to the hospital on New Earth!