The Doctor and Nyssa were kneeling beside the wreckage of the female android, poking about in eager fascination among the lumps of circuitry and silicon tubing.

'Fairly primitive,' Nyssa remarked critically, pulling the head apart with her delicate fingers and peering intently at the remains of the miniature computer.

'You think so?' murmured the Doctor, absorbed in examining the construction of the chest section.

Suddenly Nyssa held up a fused clump of wires.  'Look at this, Doctor!' she exclaimed excitedly.

The Doctor took the component and immediately sprang to his feet, calling Lieutenant Scott over to him.  'I think you should postpone your victory celebrations for the time being,' he told him.  'We must get that hatch open as quickly as possible.'

Scott gestured at the remains of the android.  'Why, Doctor?  What's the hurry?'

'One of the androids contained a powerful photosonic transmitter,' Nyssa explained, pointing to the object in the Doctor's hand.

Just then Adric joined them.  'That must have been the cause of the terrible feedback interference I picked up in the TARDIS,' he told them.

The Doctor nodded.  'Very likely.  The signals are easy to intercept, but impossible to decode without the proper receiver,' he explained.

Scott looked blankly at them.  'So?  What's the problem?'

The Doctor gave a worried frown, 'I'm afraid that whoever is responsible for that hatch over there now knows that we have destroyed its guardians.'  He turned and and scrambled over to the rocks towards the hatch.  The others followed chattering nervously.

The trpopers' lasers had burned an almost circular hole about twenty centimetres in diameter in the centre of the thick metal panel.  The Doctor knelt to investigate. Suddenly he whipped his hand away from the hot, blackened edge of the hole.  'Your squad got rather carried away didn t they, Lieutenant?' he complained, sucking his scorched fingers.  Then he took out a pen torch and shone it into the darkness, peering as close as he dared.  'I suggest that you stand well clear,' he warned them gravely after a few seconds.  'This might be booby-trapped.'

'What about you?' Scott objected, obviously reluctant to give up his authority.

The Doctor flung out both his arms like aeroplane wings.  'My arms are only this long,' he laughed, 'I can't get any further away.'  With that he resumed his examination.

Scott stirred himself.  'Right.  Everybody back!' he ordered, shepherding the onlookers across the rocks to safety on the far side of the cavern.

Only Adric was left crouching a little behind the Doctor, who gingerly pushed his arm through the hole and tried to feel about behind the panel.  For several minutes the Doctor struggled, attempting to keep his arm away from the molten edge of the hole while manoeuvring his hand inside.  'Got it!' he cried at last.  'The release mechanism.'

Then he noticed Adric.  'I thought I told everyone to get back!' he snapped angrily.

'But Doctor, it's safe.  You've checked for booby-traps,' Adric protested.

'I am not in any mood to argue!' the Doctor shouted.

Adric retreated a few paces.