Dear Rose:

I'm sitting here in the TARDIS, thinking. Well, thinking and writing. Donna's gone off to say goodbye to her mum and her grandfather, so she might be a while. I can't help but cherish this moment. I look forward to writing these letters now as often as possible. It's become a source of comfort for me, feeling the pencil beneath my fingers and the silence surrounding me as I try to tell you what I've been up to in the clearest way possible. I have all the letters I've written to you so far, they're in a small box that I keep under the TARDIS console, where nobody can find them except me. They're my greatest treasures now.

It started out as a pretty ordinary day, well, ordinary for me I guess. I was teaching Donna how to fly the TARDIS. She was quite good at it, but she almost put a dent in the 1980s!

Suddenly, I was startled to hear Martha's mobile ringing. Martha left it there in case she needed to contact me. So I answered it. It was Martha, she needed me back on Earth.

I thought Martha and Donna were going to start fighting, seeing that Martha thought Donna was her replacement. But what did they do? They start going off on me! As if I had nothing to worry about! I'm rather grateful to be skinny this time 'round mind you. Been worse before, and they have no idea! You knew though. That thought makes me smile. I'm glad you were there when I regenerated. Made my going much easier. And even after, you took it all in stride. You had faith in me.

I was startled to see how easily Martha fit in in her new position at UNIT. Donna accused me of turning her into a soldier. Maybe I did. I don't know.

So much to tell! And I don't know where to start, maybe with the Sontaran race trying to wipe out the planet for a new cloning ground, the ATMOS systems in every car poisoning the earth, or even with a young boy who made some wrong choices but in the end made everything right. I guess I'll go in that order then.

The Sontarans are a war species. They live to fight. They've been in a war with the Rutan Host for thousands of years. 50,000 years to be exact at the point of 2008 Earth time. And thousands of years after that too. I've met them before, oh yes. Don't really want to go into that right now though...

The Sontarans had secretly placed the ATMOS systems in nearly every single car on earth. Which puzzled me at first because that's not how the Sontarans do things. Usually they just blow up or invade every planet they come across. Then it hit me. The Sontarans were slowly poisoning the earth with toxious gases from the ATMOS cars, in order to prepare the earth as a breeding planet for the Sontarans. They don't reproduce normally like most species.

They also had cloned Martha in order to stop the nuclear bomb that the stupid apes at UNIT attempted to use twice! I'm sorry, I didn't mean ape. I'm still sorry I called you a stupid ape back in 1987. I regret every single mean thing I said to you now.

So, where does the young boy come in? Well, his name was Luke Rattigan. Very smart, superior intelligence above others his age. He ran a school for others like him. But he was corrupt and invented the ATMOS technology for the Sontarans. Impudent child!

I can't even begin to imagine what the Sontarans promised him in order to gain the technology, but I knew for certain, the Sontarans had no allies. Luke's pride was also his downfall.

I realized in the end that the only way to stop the Sontarans was to destroy them. But I had to give them a chance. I knew they would never take it, but I couldn't live with myself if I hadn't done so. But there was one problem. The only way I could destroy them would be to destroy myself as well. I was willing to take that chance. But it wasn't mine to take. Luke gave his life at the last minute and destroyed the Sontaran ship. Such a loss for one so young, but he made up for his past mistakes. He did something clever with the last minute of his life.

Martha and Donna were glad to see that I hadn't died. Albeit Donna was mad at first for scaring her. Just another reason to slap me I guess.

At one point, before the whole disaster, Donna told me she wanted to go home. I panicked at that moment. I couldn't imagine being alone again. That was the last thing I wanted and I desperately didn't want her to go. Then I saw the look in her eyes and realized she just wanted to go home for a visit. I'm just glad she's not leaving.

So the sky's clear of poison now, people are opting for walking instead of driving, which a good thing, and now Martha's checking on her family and Donna's saying goodbye to hers. Everything turned out alright in the end, thanks to a young boy who, although made some bad choices, saved the entire human race.

I can hear Martha at the door now, I guess I should say goodbye to her, and thanks for helping me save the world, again.

-Forever and Always-

Your Doctor