Sarah swung round.  Facing her was a squat, powerful figure about the size of a small man.  Orange-green in colour, it had small, claw-like hands and feet.  There was no neck: the big high-domed head seemed to grow directly from the bulbous torso.  The face was terrifyingly alien, with huge, malevolent green eyes and a small, puckered mouth.  A row of protuberances ran down its back.  The really horrible thing about the creature was that it seemed to be a parody of the human form.  It looked like a grotesque, evil baby.

Sarah opened her mouth to scream, but even as she drew breath the creature reached out and grabbed her with its claw.  A force like a massive electric shock slammed Sarah against the wall, and she slid unconscious to the floor.

At UNIT H.Q. the Doctor spoke into the phone, 'Sarah?  Sarah, can you hear me?'  There was no answer.  He slammed down the receiver and turned to Benton.  'Something's happened to Sarah.  We'd better get over there at once.'

Thanks to some spectacular driving by the Doctor, they arrived in an amazingly short time.  They rushe into the sick bay to find Harry's bed empty, no sign of Sarah, and Sister Lamont fluttering about in a state of great agitation.  'I assure you, gentlemen, I was only gone a few minutes.  Dr Sullivan began to talk, you see, and Miss Smith went off to call you.  I waited and waited, and when she didn't come back, I was worried and went to look for her.  I couldn't find her anywhere - and when I got back, Dr Sullivan had gone too.'

'Maybe he woke up delirious, and wandered off somewhere,' said Benton.  'I'll get some men over and search the area.'

The Doctor nodded thoughtfully.  It'spossible - but what happened to Sarah?  Sister Lamont, will you show me this telephone she used?'

While Benton used his walkie-talkie to contact UNIT, Sister Lamont led the Doctor along the spotless white corridor to a telephone fixed to the wall.  'When I came along the telephone was just swinging on its cord.  I thought it odd at the time.'

'Nobody else was on duty?'

'No.  We're just a small establishment here.'

The Doctor stood quite still, apparently lost in thought.  He nodded towards a door further down the corridor.  'Where does that lead?'

'It's a decompression unit.  We sometimes need it for the company divers.  But it's always kept locked.'  Sister Lamont seemed struck by a sudden thought.  'You know, I've just remembered, I haven't looked in the dispensary.'  She hurried off in the other direction.