PROLOGUE

The wind blew the dust across the valley as all around the wildlife hid behind whatever shelter they could find. Behind a large blue box a man and a woman stood pressed against it shivering against the wind. The man was protected against the rushing wind, dressed in a long frock coat with an equally long, trailing scarf. But the choice of clothing had been more luck than judgement. His travelling companion shivered against the bitter cold, and shot an accusing glance at her friend.

"If you poke me with that again, I'll just scream and you know how you can't stand that! Put your sonic screwdriver away," said the man. "Why is it every time you say you're going to take us somewhere nice for a well earned holiday, we end up somewhere like this?"

"That sonic screwdriver has been my constant companion for longer than you have been alive," said the woman, "and I thought this would be a good place for sand castles."

The Doctor thought it was strange speaking those words to his own body. The accidental body swap with Sarah had left them in a bit of a pickle. Sarah meanwhile was trying not to strangle herself with the Doctor's scarf. However, she felt that the worst thing was talking - how did he manage it with these teeth?

The Doctor, meanwhile, was struggling to keep his - Sarah's - teeth from chattering. "Sarah, I never really appreciated just how impractical your clothes could be until now. I'm getting breezes in the most unlikely of places."

"Never mind that, Doctor," Sarah warned. "I think we have company." They both turned to face the new arrivals - clad in furs against the weather, they seemed harmless enough, but the confusion on their faces suggested they had heard the Doctor and Sarah's conversation. They then looked at Sarah, and she realised they were waiting for some form of greeting - from the Doctor, which to all intents and purposes, was her.

"Hello," she said, approaching the leader. "We seem to have taken a wrong turning in our travels. Can you tell us where we are?"

There was a low growling noise, a splutter, more growling from one of the furry whatevers, then it coughed and a silver sphere popped out from it's body with a clang, as it fell on to the rocky terrain and rolled off into a bit of scrub wavering in the dust strewn wind.

The Doctor and Sarah watched in amazement as the silver ball, running like quicksilver, split and multiplied. Now there were nearly twenty silver spheres lying on the ground and growing until each was nearly twelve inches wide. Then as the wind continued to blow the spheres rose up and began to hover about five feet of the ground and with a high pitched squeal they all burst into flames.

"Goodness gracious, great balls of fire!" exclaimed the Doctor from Sarah's body.

"Doctor," Sarah moaned, "this is hardly the time and place for jokes." Then she saw the leader of the fur clad people approach.

"It's alright, Sarah," the Doctor assured her. "We're among friends."

"But. . . "

"That joke was actually a greeting," he explained. "And now I know where we are. This is the planet Atora, and these are its inhabitants, the Choorall."

"You might have warned me," Sarah admonished him.

"The Doctor is correct," announced the Choorall leader. "We are a peaceful people."

Now it was the Doctor's turn to be amazed. "You recognise me?"

"You are a Time Lord," came the simple reply. "We know of the process of regeneration, as should your male companion."

"Ah." Sarah stifled a giggle as the Doctor realised the Choorall's mistake. "I think I need to explain a few things first."

Just at that moment, a black triangular void, at first quite small, but enlarging at a tremendous rate, came scooping out of the storm cloud filled sky and enveloped the Doctor, Sarah and the TARDIS. Seconds later, the Choorall were staring at an empty space where the ship and its gender swapped occupants had been standing.