Season 1, Episode 5 - "The Dead Planet"
11 April, 1964
The ship has arrived in a petrified forest on an apparently dead planet. Exploring, the travellers see a fantastic city in the distance. The Doctor wants to investigate further, but Ian and Barbara veto this idea, insisting that they return to the TARDIS. The old man eventually gets his own way by resorting to a trick: he claims that one of the ship's vital components, a fluid link, needs refilling with mercury, and that the only place this might be found is the city.
