After the first two stories, this one comes as a bit of a shock. After the explosion inside the TARDIS at the end of The Daleks, everything inside the ship is strange in the extreme.
All the travellers are at odds with each other not even recognising each other at first. At different times accusing, suspicious, even attacking each other. Feelings that have been deeply hidden are brought to the surface. The TARDIS itself is behaving very oddly. Pictures on the scanner that aren’t real, the fault locator not showing any fault, then saying that the ship is close to disintegration.
To the point that the Dr. says they only have 5 minutes left !
They eventually find that a switch on the console has got stuck. Once fixed the crisis is over and they return to normal flight through the space/time vortex……
Although only 2 episodes there has never been anything else like in it Dr. Who history. The acting of the 4 leads is very convincing and makes the story compelling.
The only odd thing is that the whole cause of the problem was a stuck spring.
Next Episode : The Roof of the World
peterjfield 
i love it