Hermione: she might trouble about him, and he did not want the onus of this. So at the station, he wrote saying:

I will go on to town — I don’t want to come back to Breadalby for the present. But it is quite all right — I don’t want you to mind having biffed me, in the least. Tell the others it is just one of my moods. You were quite right, to biff me — because I know you wanted to. So there’s the end of it.

In the train, however, he felt ill. Every motion was insufferable pain, and he was sick. He dragged himself from the station into a cab, feeling his way step by step, like a blind man, and held up only by a dim will.

For a week or two he was ill, but he did not let Hermione know, and she thought he was sulking;