'So who is it?' demanded Random.

'She is part of the extent of your mother on the probability axis,' said the bird Guide.

'I haven't the faintest idea what you mean.'

'Space, time and probability all have axes along which it is possible to move.'

'Still dunno. Though I think . . . No. Explain.'

'I thought you wanted to go home.'

'Explain ! '

'Would you like to see your home?'

'See it? It was destroyed!'

'It is discontinuous along the probability axis. Look!'

Something very strange and wonderful now swam into view in the rain. It was a huge, bluish-greenish globe, misty and cloud-covered, turning with majestic slowness against a black, starry background.

'Now you see it,' said the bird. 'Now you don't.'

A little less than two miles away, now, Arthur Dent stood still in his tracks. He could not believe what he could see, hanging there, shrouded in rain, but brilliant and vividly real against the night sky – the Earth. He gasped at the sight of it. Then, at the moment he gasped, it disappeared again. Then it appeared again. Then, and this was the bit that made him give up and stick straws in his hair, it turned into a sausage.

Random was also startled by the sight of this huge, blue and green and watery and misty sausage hanging above her. And now it was a string of sausages, or rather it was a string of sausages in which many of the sausages were missing. The whole brilliant string turned and span in a bewildering dance in the air and then gradually slowed, grew insubstantial and faded into the glistening darkness of the night.

'What was that?' asked Random, in a small voice.

'A glimpse along the probability axis of a discontinuously probable object.'

'I see.'

'Most objects mutate and change along their axis of prob– ability, but the world of your origin does something slightly different. It lies on what you might call a fault line in the landscape of probability which means that at many probability co-ordinates, the whole of it simply ceases to exist. It has an inherent instability, which is typical of anything that lies within what are usually designated the Plural sectors. Make sense?'

'No. '

'Want to go and see for yourself?'

'To . . . Earth?'

'Yes.'

'Is that possible?'

The bird Guide did not answer at once. It spread its wings and, with an easy grace, ascended into the air and flew out into the rain which, once again, was beginning to lighten.

It soared ecstatically up into the night sky, lights flashed around it, dimensions dithered in its wake. It swooped and turned and looped and turned again and came at last to rest two feet in front of Random's face, its wings beating slowly and silently.

It spoke to her again.

'Your universe is vast to you. Vast in time, vast in space. That's because of the filters through which you perceive it. But I was built with no filters at all, which means I perceive the mish mash which contains all possible universes but which has, itself, no size at all. For me, anything is possible. I am omniscient and omnipotent, extremely vain, and, what is more, I come in a handy self-carrying package. You have to work out how much of the above is true.'

A slow smile spread over Random's face.

'You bloody little thing. You've been winding me up!'

'As I said, anything is possible.'

Random laughed. 'OK,' she said. 'Let's try and go to Earth. Let's go to Earth at some point on its, er . . .

'Probability axis?'

'Yes. Where it hasn't been blown up. OK. So you're the Guide. How do we get a lift?'

'Reverse engineering.'

'What?'

'Reverse engineering. To me the flow of time is irrelevant. You decide what you want. I then merely make sure that it has already happened.'

'You're joking.'

'Anything is possible.'

Random frowned. 'You are joking aren't you?'

'Let me put it another way,' said the bird. 'Reverse engineering enables us to shortcut all the business of waiting for one of the horribly few spaceships that passes through your galactic sector every year or so to make up its mind about whether or not it feels like giving you a lift. You want a lift, a ship arrives and gives you one. The pilot may think he has any one of a million reasons why he has decided to stop and pick you up. The real reason is that I have determined that he will.'

'This is you being extremely vain isn't it, little bird?'

The bird was silent.

'OK,' said Random. 'I want a ship to take me to Earth.'

'Will this one do?'

It was so silent that Random had not noticed the descending spaceship until it was nearly on top of her.

Arthur had noticed it. He was a mile away now and closing. Just after the illuminated sausage display had drawn to its conclusion he had noticed the faint glimmerings of further lights coming down out of the clouds and had, to begin with, assumed it to be another piece of flashy son et lumiЉre.

It took a moment or so for it to dawn on him that it was an actual spaceship, and a moment or two longer for him to realise that it was dropping directly down to where he assumed his daughter to be. That was when, rain or no rain, leg injury or no leg injury, darkness or no darkness, he suddenly started really to run.

He fell almost immediately, slid and hurt his knee quite badly on a rock. He slithered back up to his feet and tried again. He had a horrible cold feeling that he was about to lose Random for ever. Limping and cursing, he ran. He didn't know what it was that had been in the box, but the name on it had been Ford Prefect, and that was the name he cursed as he ran.

The ship was one of the sexiest and most beautiful ones that Random had ever seen.

It was astounding. Silver, sleek, ineffable.

If she didn't know better she would have said it was an RW6. As it settled silently beside her she realised that it actually was an RW6 and she could scarcely breathe for excitement. An RW6 was the sort of thing you only saw in the sort of magazines that were designed to provoke civil unrest.

She was also extremely nervous. The manner and timing of its arrival was deeply unsettling. Either it was the most bizarre coincidence or something very peculiar and worrying was going on. She waited a little tensely for the ship's hatch to open. Her Guide – she thought of it as hers now – was hovering lightly over her right shoulder, its wings barely fluttering.

The hatch opened. Just a little dim light escaped. A moment or two passed and a figure emerged. He stood still for a moment or so, obviously trying to accustom his eyes to the darkness. Then he caught sight of Random standing there, and seemed a little surprised. He started to walk towards her. Then suddenly he shouted in surprise and started to run at her.

Random was not a good person to take a run at on a dark night when she was feeling a little strung out. She had unconsciously been fingering the rock in her pocket from the moment she saw the craft coming down.

Still running, slithering, hurtling, bumping into trees, Arthur saw at last that he was too late. The ship had only been on the ground for about three minutes, and now, silently, gracefully it was rising up above the trees again, turning smoothly in the fine speckle of rain to which the storm had now abated, climbing, climbing, tipping up its nose and, suddenly, effortlessly, hurtling up through the clouds.

Gone. Random was in it. It was impossible for Arthur to know this, but he just went ahead and knew it anyway. She was gone. He had had his stint at being a parent and could scarcely believe how badly he had done at it. He tried to continue run– ning, but his feet were dragging, his knee was hurting like fury and he knew that he was too late.

He could not conceive that he could feel more wretched and awful than this, but he was wrong.