"Only to-day?" said the Doctor.

"Oh, I've been feeling better and better, but to-day it's as if a door that had been creaking on its hinges was flung wide open."

"I'm not surprised. These sudden leaps forward are often a feature of convalescence."

"They--they aren't followed by falling back, are they?" Nigel asked, with a sudden change to uneasiness.

"Sometimes, in fever cases especially. But in a case like yours we needn't anticipate anything of that kind."

The last words seemed to suggest to Nigel some train of thought, and after sitting in silence two or three minutes, looking grave and rather preoccupied, he said: "By the way, what has been the matter with me, exactly? What have I really had in the way of an illness? All this time I've been so occupied in being ill that I've never asked you."

The last words were said with an attempt at lightness.

"Have I?" he added.

"No, I don't think you have," said Isaacson, in a voice that suggested a nature at that moment certainly not inclined to be communicative.

"Has it been all sunstroke! But--but I'm sure it hasn't."

"No, I shouldn't put it down entirely to sunstroke. Hartley wasn't quite right there, I think."

"Well, then?"

Nigel had found a safe topic for conversation, or thought he had. It was sufficiently evident that he felt more at ease, and perhaps he was atoning for former indifference as to the cause of his misery by a real and keen interest about it now.