The Edge Of Destruction was the two part story that followed The Daleks and was set entirely in the Tardis. The Story itself was written in two days as a hasty “filler” story to enable the series to fit a thirteen episode run. At this point in time it was all the time the series had been granted.
Attempting to correct the TARDIS’s faulty navigation circuits, The Doctor causes a small explosion. Temporarily rendering himself and the crew unconscious.
As they awake, Ian and Susan appear to have slight cases of amnesia and everyone begins to act strangely. Unexpected events are happening in the TARDIS. The travellers become suspicious of each other’s motives, and the Doctor even accuses Ian and Barbara of sabotage.
Fearing that they have been taken over by some alien force — or that they have intentionally sabotaged the TARDIS in order to force the Doctor to return them to 1963 —The Doctor drugs Barbara and Ian unaware that Ian is also suspicious and has not taken the drink given to him.
As The Doctor attempts to explore the problem without interference, it becomes clear that the strange events are the TARDIS’ way of warning it’s crew something is wrong. A malfunction caused by a problem with the fast return switch is to blame and repairing it brings things back to normal.
Carole Ann Ford
Written By: David Whittaker
Produced By: Verity Lambert
Original Run: February 8-15 1964