The TARDIS materialised in a dim room with a moaning wheeze. The only light came through a massive observation window from a planet smothered in sickly yellow clouds. After the space / time craft finally became completely solid and tangible, the room's motion detector switched on the lights. A few moments later, two figures emerged from what looked like a blue Police Box.

The taller of the two figures, a man with short-cropped hair and a leather jacket, looked out the observation window. He said nothing, simply stared. The other, a pretty blond named Rose, looked around.

Rose said, "Doctor, I think we arrived at the wrong place again."

The Doctor gave no answer. He simply continued to stare out the observation window.

"What's wrong, Doctor?" asked Rose. "After what..."

Without taking his gaze from the window, the Doctor replied, "Earth hasn't always been my favourite planet. Early on in my travels, I visited the planet before us - Venus - as it was three billions years before your time. It was fantastic. So wonderful."

"Venus was inhabited? Wasn't it too hot for life?"

"Not back then," replied the Doctor. "But even then, three billion years ago, the writing was on the wall, so to speak. The planet's rotation was slowing down, which in turn caused the average temperature to increase. Around the time of my first visit, it seemed like the Venusians had just over a century left to them. Later on, they used co-ordinated volcanic eruptions to cool the planet and eke out another ten thousand years, but at the time it seemed like they had just a century. It was so sad. Susan had wanted me to save them. She begged me to. But I didn't."

Rose had two questions. "Why not? And who's Susan?"

"You could say that Susan was my granddaughter," replied the Doctor. "Like the rest of my people, she's gone now."

"I'm sorry," said Rose.

The Doctor closed his eyes for a minute. Then he said, "I thought about doing what Susan had asked, saving the Venusians. I thought about it hard, but I couldn't do it."

"Why not?" demanded Rose.

"Because the only way that I could have saved them was to help them migrate to Earth," replied the Doctor. "If the Venusians would have done that, humanity would have never come into existence. I let them die so that you and your kind could live. It wasn't a fun choice."

"Thank you," said Rose, unable to think of anything else to say.

"Earth was lucky that the Venusians even needed my help to survive," mused the Doctor. "If metal had not been poisonous to them, they could have saved themselves, and you wouldn't be here. If I recall correctly, my first ever visit to Earth was to show Susan what would've been lost if we had saved the Venusians. We took our friend Dharkig, a great philosopher if there ever was one, with us. I wanted him to understand why I wouldn't help his people. Upon seeing Earth, he started to urge his people to accept the inevitable with grace and dignity. Since the Time War, I have tried to do the same. But I'm no Dharkig."

"He sounds like a great man," said Rose respectfully.

"He was fantastic," agreed the Doctor. "He was a great person, but hardly a man. He was giant reptile-like creature with five legs."

"Your friends certainly come in all shapes and sizes," remarked Rose.

"I do enjoy a fantastic variety when it comes to my friends," replied the Doctor. "Come on, let's see if anyone is aboard this satellite."

"Okay."

When the Doctor reached the door, he exclaimed, "Wow!"

"What?"

"Can't you see?" demanded the Doctor. "TVP has been written on the door!"

"Doctor, are you sure you're feeling all right?" Rose asked, growing concern obvious in her voice.

"Fine," replied the Doctor. "I forgot that TVP would mean nothing to you. During my last incarnation, I spent over a century on Earth, without any memory of my origins. That was before we managed to restore Gallifrey, just so the..."

"Doctor," said Rose sympathetically as her friend trailed off.

"Sorry," said the Doctor, pushing his melancholy aside. "Near the end of that time on Earth, I set up this company, The Venus Project. It was to terraform Venus when it became possible to do so. Until then, it was supposed to research and develop the technology it would ultimately need. It was also to distribute half its profits to a couple of charities that had been really near and dear to my hearts. Most of the other half was to go to more research. I had forgotten all about setting up this outfit! Let's go see the tree that grew from the seed I planted."

The Doctor led Rose through the door, and out into the corridor beyond. The two of them started to explore the satellite. As they walked though its silent corridors and looked into its rooms, motion detectors turned on lights for them. Ten minutes into their inspection, they still had yet to encounter anyone. Despite the apparent absence of any crew, everything seemed undamaged and in its proper place.

"This is weird," said Rose.

The Doctor nodded, and then led them through a door that opened out on a catwalk. The metal walkway stretched out across and above a massive, flooded chamber to another door. The centre of the catwalk bulged into a circle to provide space for a workstation and ladder leading up. Fans, interspersed among the lights in the ceiling, could be heard working. Green slime covered the gently rippling water below the catwalk.

"What's this room for?" asked Rose.

"This is the heart of the operation," replied the Doctor. "In here blue-green algae is grown. I'm sure that this algae is seeded into Venus' clouds, probably by robotic space-planes. At least, that was my plan. There it will start using up carbon dioxide and producing oxygen. Given enough time, that will make Venus' atmosphere suitable to human life, as well as making the planet cooler."

"Cooler?" asked Rose.

"Yes," replied the Doctor. "Carbon dioxide is a major greenhouse gas."

Before they had reached the middle of the enormous room, and the Doctor stopped. "I think I'll take a moment to catch my breath."

Rose glanced nervously at the Doctor. "Maybe we should return to the TARDIS."

"No need," replied the Doctor. "I'm fine now."

The two then continued on toward the workstation in the centre of the room. Before they could reach it, a long, slender fish almost surreally gold in colour leapt out of the water and over the catwalk not far in front of them. Rose yelped in surprise, and the Doctor's eyes widened with astonishment.

"That was a gold usher fish if I ever saw one!" exclaimed the Doctor.

"A what?"

"A gold usher fish," replied the Doctor. "They're a rare fish from Gallifrey! What's it doing here?"

"Maybe it's your pet," mused Rose. "A future you, I mean. Maybe an older you was in charge of this station, and that's why everyone's cleared out. So the two of you won't meet. That whole not changing the past thing."

"Maybe," said the Doctor, sounding dubious. "One way to find out!"

With that, the Doctor sprinted to the workstation. At a more sedate pace, she made her way over to him.

When she got there, the Doctor said, "I think I might have found the answer. About two hours ago, the satellite received a message from a spaceship on an intercept coarse. I'll play it."

The Doctor and Rose turned their attention to the workstation's monitor. It showed the image of a man with a lean build, cream-coloured skin, and large brown eyes like two discs of wood. Oddly, in addition to what looked like a silver flight-suit, he had on a feather head-dress like the ones worn by some Native Americans.

The man said, "Crew of the Venus Project Satellite, I am True Spirit and I am calling to give you all fair warning. As we now know, Venus was once a world that harboured life, but no longer. Now Venus is the sacred resting place of that life. What you are doing - trying to turn Venus into just another thing for humanity to exploit - is a vile sacrilege, one that I cannot and will not allow. So I'm going ram my ship into your satellite and blow it from the sky. Then my soul will join with those already resting in Venus' spirit realm. So I advise you all to abandon your satellite, unless you want to join me in the hereafter."

The monitor went blank. "What a nutter!" exclaimed Rose.

"But apparently one the crew of this satellite took seriously," said the Doctor. "I'd better try to contact him, and make him see reason."

"Good luck," said Rose sceptically. This True Spirit hardly seemed the sort to see reason.

For several minutes, the Doctor tried to contact True Spirit, but to no avail. "He's ignoring me," said the Doctor.

"What are you going to do?"

"I'm not going to let him blow up this fantastic satellite and what might be the last gold usher fish in the universe," declared the Doctor. "Besides, he'll be here almost before we could get back to the TARDIS. I'm going to have to stop him."

"How are you going to do that?" asked Rose.

"He leaves me no choice." The Doctor's voice was grim. Rose could tell that he was stealing himself to do something drastic. "I'll have to use one of the satellite's robot space-plane as a missile and blow him out of the sky."

"He's bent on dying anyway," said Rose, but the Doctor was no longer listening. He was typing furiously at the workstation, trying to get one of the satellite's space-planes to do what he needed it to do. Long minutes passed. Rose could only watch, and hope for the best.

The Doctor suddenly started to swear in Venusian.

"What's wrong?" demanded Rose.

Without taking his eyes from the computer screen, the Doctor replied, "Another spaceship seemingly appeared out of nowhere and blew up my space-plane. I think it's our 'friend' from Antarctica. He must want the satellite destroyed, knowing that the TARDIS would survive the explosion."

"What do we do?" asked Rose.

The Doctor looked up from the computer screen, and Rose could see the anger in his eyes. "We run!"

So the Doctor and Rose raced back to the TARDIS as fast as they could. Despite his earlier tiredness, the Doctor set a punishing pace that Rose almost couldn't match. Not far from where they had arrived, Rose slipped and fell. She tried to get up, but the Doctor picked her up and slung her over his shoulder before she could. Almost before she knew it, they were inside the TARDIS. After lowering her gently to the ground, he bolted for his controls, and started operating them almost faster than the eye could follow.

Then the Doctor stopped and stepped back from the console. "We're safe now, but the satellite is gone, along with the gold usher fish," he announced.

Rose could only say she was sorry.

"Perhaps they will rebuild," said the Doctor. "Or maybe that had already done enough. In any case, I already know that Venus will someday once again enjoy life. It just would've been fantastic to have been the reason why."

"Maybe you are," said Rose. "Or should that be were?"

The Doctor smiled. "It depends on who you ask."

"Where to now?" asked Rose.

"I have no idea," replied the Doctor. "To make sure we escaped in time, I had let the TARDIS take us where it will."

"Here we go again," muttered Rose.