A little boy goes missing; a policewoman begins drawing cave paintings; and the employees at the mysterious Glasshouse are desperate to keep everyone away -- the Doctor suspects it's all down to a group of homo reptilia. His assistant, Liz Shaw, has ideas of her own and has teamed up with a journalist to search for people who don't exist. Behind it all lies a conspiracy to exploit UNIT's achievements -- a conspiracy reaching deep into the heart of the British Government.
Liz shook her head. 'I don't know. I came in this morning and he was seated exactly where I'd left him last night. I don't think he's slept a wink.'
The Doctor swivelled round, the hot soldering iron pointing at them like some kind of alien weapon. 'My dear Liz, sleep, as a wise man once said, is for tortoises. And if you must know, Lethbridge-Stewart, I'm actually obeying your orders for once.' He got up, placed the soldering iron on its rest and let his jeweller's eye-glass drop into his hand. 'As usual, the two of you have been so absorbed in chit-chat that you've failed to notice an important omission from this lab.' He had crossed the room and was standing face to face with the Brigadier. Taking the military officer's swagger-stick, he twirled it like a magician's wand and tapped the side of his head. 'Worked it out yet?'
Liz stared around for a moment and gasped. 'That TARDIS console. It's gone!'
The Doctor smiled at her. 'Well done, Liz. Top of the class.' He shot a look back a