Doctor Who and the Planet of the Spiders

Hodges into unconsciousness. Lupton turned and ran for the
door into the main building.
‘So you see,’ the Doctor was saying, ‘poor Professor Clegg
saw spiders before he died, and you saw spiders at the
monastery. There must be a connection. And it has to be this
crystal!’
Sarah looked at the blue gem, sitting incongruously amongst
the tangle of electronic equipment. ‘Where did it come from
anyway?’
‘I brought it back some time ago, from a planet called
Metebelis Three.’
Briefly, the Doctor told Sarah the history of the jewel, and of
its strange power to affect the mind.
‘You mean it could, well, drive someone mad?’
‘Just the opposite. It clears the mind, and amplifies its
powers.’
‘But it could be used for evil purposes?’
‘Oh yes. If the minds using it were motivated by evil...’
Sarah shivered. ‘The minds of the giant spiders on Metebelis
Three?’
‘That’s just it,’ said the Doctor. ‘There aren’t any.’
In the corridors nearby, Lupton moved cautiously on his
way. ‘Nearer,’ said the voice of the Spider inside his head. ‘We
are getting closer – we are almost there.’ Following its directions,
Lupton came nearer and nearer to the Doctor’s laboratory.
Suddenly, a big man in army uniform came round the corner
and stood in front of him.
‘Excuse me, sir, you’re in a security area. May I see your
pass?’
Lupton ignored him, and went on. Sergeant Benton was
outraged. Automatically, he drew his revolver. ‘Halt, or I fire!’
Lupton swung round and stretched out his hand. Benton was