Nothing else
There were no reasons for him to stay.
He'd always tried to make his parents understand his choices, but they wouldn't listen to anything: Sirius knew they were sickened of their own son, that they hated him being a Gryffindor, but he'd learnt not to care.
Bearing his parents' offences turned out to be much more difficult than he had expected and he'd lost his temper so many times that it was almost normal for the Blacks to see their eldest son slamming the door - shouting he would never come back - and disappearing for one or two days.
It had just happened.
Sirius wandered in London, thinking.
What if I just don't come back? They won't miss me.
He entered the Leaky Cauldron and sat as far as possible from the other people: they were too cheerful and noisy for his mistreated soul. He felt like he'd rather stop and die on that uncomfortable chair than coming back home to face his parents' harsh words, and his brother's reproachful looks.
Regulus could be really annoying and Sirius didn't want to see his usual grimace of pride and triumph - it felt so right just to leave them all and live a better life.
After all, he had James Potter, his best friend.
His brother.
Their souls were entwined by something which went beyond their grasp and they treasured it as the most valuable thing they owned: Sirius had sworn to himself he'd rather die than betray James.
And he was sure James would do the same, because he'd learnt how to read in his eyes.
He was everything to him.
For that very reason, Sirius was ringing at the Potters' door, while the sunset drowned his features in red-blood light.
James felt a strange stab in his stomach when the bell rang, as something really heavy had just left him forever: it was a sweet sensation, and he half swayed to the door with unusual lightness.
-What the… Sirius?- he shouted, stunned. Sirius had never come to his house, and James instantly understood that something strange had happened.
-James… I just… you know, escaped…- Sirius whispered, staring at him as though he was hanging to his eyes not to fall.
-Escaped! From your parents'! You… well, come in… and tell me… What the ruddy hell happened?-
-Fought. They insulted me. I can't stand it anymore, you know. So… I thought of you. Well, if you don't want to put me up...- Sirius looked around, clearly at unease: the more he stayed there, the more stupid he felt.
-Like I wouldn't give you a place to stay.- James laughed. -Don't be ridiculous, Sirius, you can stay here how long you want. I'll go and tell my parents. You can camp in the garden.
There was nothing else to be said.
James didn't want any 'Thank you's, because he could hear gratefulness echoing in Sirius's words and see it etched in his suffering eyes, in his rebel gaze.
Anyway, Sirius couldn't let it happen.
After a long dinner, when the night had fallen, as fresh as water, on their beaming faces, Sirius hugged James, then laughed.
Now there was nothing else to say.