-Yeah, it seems to be nice that someone comes here after all this time. But... why? 

-I've come to kill you and free the world 

-Why? You're already dead. Everyone is dead. Don't you get it? Doesn't matter what you do, it's a thing of time. This one is going to crush the other, and it's going to be exterminated in the impact. Also the other is going to be destroyed, but human race it's like this. They can't see that working together it's better than fighting each other. That's why I'm here. I am the one that holds everything in its place. Without me, humans will last minutes. Eight, concretely. That's the time they will need to see that their beloved sun is not working. So, that's why you can't kill me. If you kill me, you will doom your own race. 

-no, there's something I can do

-what?

-I can take your place and lead the humanity into other path, a brighter path. The problem it's not the man, it's the man's mind, and I can change their mind. I can change it since the beginning of times, and the two of us will be all right, because there wasn't any motive for us to kill each other. 

-you are so incredibly ingenuous. Doing that will only get us in a temporal glitch. If you never had to kill me, then you couldn't change the world, so you'll be alright and you will come to kill me, so you will change the past. If you do that, there will be really any form of saving humanity. It's your decission.