From somewhere up above him, he thought he heard a ghostly chuckle of laughter, and looked up in alarm but he could see nothing there.

Nothing, that is, except the last traces of mist, still hanging about the tree tops and, before his astonished gaze, two faint, floating letters half-shrouded in the mist.

An 'm' and a 't', both with a diagonal stroke through them, as if they had been crossed out.

'Wait a bit... I've seen something like that, somewhere before,' he said to himself.

Then he looked again at the cut-out hand, which also had a letter written upon it the letter and saw that this too had been crossed out and cancelled.

'It's very puzzling,' he mused and suddenly slapped his forehead. 'Ye G.o.ds, I need my brains taken out and b.u.t.tered I must be losing my grip. A puzzle! Of course that's what it is a picture puzzle a rebus.'

It was the sort of thing one sometimes finds in children's comics or annuals; a sentence made up of pictures, where each picture represents a word, if one can interpret them correctly.

Hopefully, the Doctor began to put the images into the correct order: first Jamie poor, faceless Jamie... Then the misty letters, the safe, the hand, the wishing well.

But the 'm' and 't' had been blotted out from the mist so 'mist' became 'is'... Just as 'hand' without the 'h' became 'and'.

At once the whole thing fell into place.

' Jamie... Is... Safe... And... Well. Jamie... Is... Safe... And... Well. ' '

As the Doctor repeated the five words aloud, there was one final clap of thunder, and a flash of lighting: and Jamie came to life again.

'Hey, Doctor!' he exclaimed joyfully, grabbing the Doctor's hand and shaking it vigorously. 'I'm certainly glad to see you I thought for a while I'd lost you for good!'

The Doctor withdrew his hand, confused and ill-at-ease.

For the voice was Jamie's voice he was in no doubt about that but the face was somehow unrecognisable. Were those really Jamie's eyes? Was his mouth quite so wide or his chin so pointed?

Before he could stop himself he blurted out in dismay: 'I must have got it wrong. You're not Jamie!'

The Scottish boy grinned: but it was a stranger's grin.

'What are ye on about now?'

'Well you your face it it's different... '

'How d'ye mean different?'

The Doctor fumbled in his pocket and brought out a small hand-mirror, which he pa.s.sed over.

'See for yourself.'

Jamie looked at his unfamiliar reflection and recoiled; 'That's no my face I've never seen it before in my life.'

'Maybe not,' sighed the Doctor, 'but it seems to be the one you're stuck with at present so we'll both have to get used to it.'

'But why? How did it happen?'

'All I can tell you is that it's a particularly nasty trick on the part of the person who brought us here,' replied the Doctor and he looked up at the sky, accusingly.

This time there was no question about it: he heard a far-off shout of gleeful, malicious laughter... The Master whoever he might be was obviously most amused at this turn of events.

From now on, the Doctor realised, he could no longer trust anything that might happen or that might seem to be happening. Everything was a minefield of tests and traps and practical jokes: and appearances were always deceptive.

'How do I know you are Jamie?' he enquired bitterly.

'How do I know you're not another illusion sent to confuse me still further?'

'Of course I'm Jamie!' snorted the boy, indignantly. 'I told you so I'm still me even if I can't recognise myself!'

'But how do I know I can believe you?' the Doctor persisted. 'Can you prove to me that you're Jamie McCrimmon? Where have you come from? How did you get here?'

Jamie scratched his head, and tried to remember.

'It's hard to say...It's all a wee bit hazy... The last thing I really remember clearly is a dream I had.'

'A dream?'

'Aye I was telling you about it when I woke up, don't you remember? We were in the TARDIS: I'd been s.n.a.t.c.hing forty winks, and in my dream there was this beautiful white unicorn... Beautiful but frightening because the dream turned into a nightmare. The unicorn lowered its head and began to charge at me pointing its horn towards me as if it would run me through... '

The Doctor's brow cleared: and he smiled with relief.

'Yes now you mention it, I do do remember you telling me about that dream. But what happened next?' remember you telling me about that dream. But what happened next?'

'Well, there was this unicorn head down, ready for the kill and then everything went crazy, and I was off.'

'Off? Off where? Where have you been?'

'In a fog... I mean really really in a fog. Ever since the TARDIS in a fog. Ever since the TARDIS broke up.'

The Doctor repeated his words automatically: 'Ever since the TARDIS broke up ' and suddenly realised what he was saying. 'It did what what?'

He grabbed Jamie's arms, and demanded: 'What are you telling me? What's happened to the TARDIS?'

'It broke up fell to bits I thought you knew that... We all flew off into s.p.a.ce and then somehow we finished up here. You, me and ' He hesitated, looking around, then said in a small voice: 'And Zoe... ? Where is she?'

The Doctor looked very grave. 'I wish I knew. I suspect she's been caught up in some sort of trap just as we have.'

'A trap? What sort of trap?' He stared at the towering tree trunks that surrounded them. 'Where exactly are we, anyway?'

'I can't tell you, I'm afraid. All I can tell you is that wherever we are we were expected. There's been quite a welcoming committee prepared to meet us.'

Jamie scratched his head, completely bewildered.

'How do you mean?'

'We were brought here as part of a plan, by someone who calls himself the Master, apparently. But what or where he is Master of, I have yet to discover. The only thing I know for sure is that he enjoys setting puzzles brainteasers tricks and riddles.'

'Riddles?' The boy still looked blank. 'I don't understand.'

'You will, Jamie you will.'

And as if to ill.u.s.trate this point, they were interrupted by a plaintive call for help a m.u.f.fled voice, that seemed to be coming from inside a prison: ' Doctor Jamie help me! Doctor Jamie help me! ' '

Jamie's head snapped up instantly: 'There she is that's Zoe!'

The Doctor shouted as loudly as he could: 'Yes, Zoe we hear you where are you?'

The reply came in the same indistinct tone: 'I'm trapped I can't get out please help me!'

Jamie began to run towards the source of the sound, exclaiming: 'I think she's over here somewhere!'

The Doctor set off at a jog trot after him, both of them weaving their way along the winding paths that snaked through the tall trees. As the Doctor had realised earlier, the strange formation of closely-planted trees made an excellent hiding place but when you were trying to find someone lost in that maze, it presented problems.

They searched here and there, down long alleys that led off into darkness, and time and again came up short against a huge tree trunk blocking their path. Only Zoe's encouraging cries spurred them on.

It was like one of those tantalising nursery games of 'Hunt the Thimble'; as Zoe's voice got louder or fainter, they felt the trail growing 'hot' or 'cold'.

Then, quite suddenly, they turned a corner, and knew they were at their journey's end.

They had reached an old oak door set in a blank wall: a heavy door, studded with bolts, under a gothic arch. And from the other side of the door, Zoe's voice called desperately: 'I can't get out... Help me please!'

Jamie put his shoulder to the timbers and tried to shove but it was impossible: the door wouldn't budge an inch.

'There's no handle,' he grumbled, searching for some way to tackle it. 'No sign of a lock either.'

The Doctor ran his fingertips over the surface of the wood, and said, 'It's hardly surprising when you consider that this isn't even a real door. Don't you see? It's another illusion a wall, with a door painted on to it.'

Jamie scratched at it with his fingernails. The Doctor was right. It was not wood, but solid, unyielding stone.

'But that's crazy!' he exploded. 'How can anyone get through a door that isn't a door?'

His words rang a bell somewhere at the back of the Doctor's mind... A door that wasn't a door...

'Give me a moment to think ' he muttered, ma.s.saging his temples, as if he were trying to press his brain on to greater efforts. 'I must think think... '

'What's the good of thinking?' Jamie stormed impatiently. 'What we want is a battering ram maybe if we could cut down one of those trees '

But the Doctor wasn't listening. 'When is a door not a door?' he asked, with a chuckle.

'Och this is no time for riddles - 'That's where you're wrong! I told you this is is a time and a place for riddles! When is a door not a door? When it's ajar!' a time and a place for riddles! When is a door not a door? When it's ajar!'

As he answered the riddle the solid-looking door melted away into mist, and through it they saw Zoe her dark hair dishevelled, her silver jumpsuit curiously distorted trapped inside a huge, transparent jar, and beating her fists against the gla.s.s.

Jamie began to laugh: he couldn't help it for she really did look rather comical. 'At least that's kept you out of mischief for a while!' he commented.

'Oh, you !' Zoe was crosser than ever. 'Get me out of here!'

It didn't take long. The Doctor gave Jamie a leg-up and he climbed to the top of the jar, then leaned over and stretched down, holding out his hands to Zoe.

She clutched at him, and he hauled her up. A moment later, they had both scrambled down again, and she was free.

'Oh thank goodness!' she panted. 'I began to think I was never going to get out of there.'

She dusted herself down, and then took a closer look at her rescuer and her face changed. 'Just a minute you're not Jamie. Who are you?'

He groaned: 'Don't you start I've had enough trouble from the Doctor already... I tell you I'm Jamie McCrimmon I'm me!'

Zoe turned to the Doctor for confirmation. 'But why does he look so different?' she asked.

The Doctor examined his fingernails uncomfortably, and cleared his throat: 'Uh er a slight technical hitch, my dear... I'll explain later. First of all, I think we should get out of this forest, don't you?'

Jamie nodded vehemently: 'The sooner the better this place gives me the shivers... Come on I'll lead the way.'

He set off among the trees at a brisk pace, and the others followed a little more slowly. Zoe clutched at the Doctor's sleeve and whispered: 'Is that really really Jamie? Are you quite sure?' Jamie? Are you quite sure?'

The Doctor said sadly: 'Oh, yes, it really is... He's just changed a little that's all.'

'But he couldn't have! It's impossible!'

'I think, Zoe, that we are now in a place where nothing is impossible. Come on we don't want to lose him again.'

They trudged on and on through the forest, hoping to find a way out, but without any success. The tall trees seemed to stretch on into the distance for mile after mile and at last Zoe called a halt.

'I don't care what you say I want to sit and rest for a while. I had to stand up inside that beastly jam jar, because there wasn't enough room to sit down and my feet hurt!'

She flopped down on the ground then and there, sitting with her back to one of the smooth tree trunks.

Jamie looked up at the treetops, squinting, and shielding his eyes against the light. 'It's very strange,' he said thoughtfully. 'I don't know if you've noticed it, Doctor, but these trees don't seem to have branches or leaves. They just stretch up into the sky, and then stop dead. If you could give me a leg up again, I might be able to climb up and see what's what.'

The Doctor agreed it was worth a try: 'You might be able to see a way out of the wood from the top... As things are down here, we can't see the wood for the trees to coin a phrase.'