Robert Holmes added the scene where The Doctor shows Sarah how the events of 1911 can effect her future, because felt that this would help offset the general presumption by viewers that threats encountered in historical stories didn't matter, since modern-day Earth has been seen to endure in other Doctor Who serials.
This episode was watched by 11.3 million viewers on its original transmission.
This episode takes place in England in 1911 and 1980.