Isaacson did not reply for a moment.

“Perhaps sometimes they do,” he answered at last.

“And don’t you think they require sacrifices?”

“Do you mean human sacrifices?”

“Yes.”

“Perhaps—­sometimes.”

“Why have you never been to call on Mrs. Chepstow?”

Again the sallow fingers began to play with the book-covers, passing from one to another, but always slowly and gently.

“I haven’t much time for seeing any one, except my patients, and the people I meet in society.”

“And of course you never meet Mrs. Chepstow in society.”

“Well—­no, one doesn’t.”

“She would have liked a visit from you, and she’s very much alone.”

“Is she?”

“Are you stopping on much longer in London?”

“Till the twelfth or fifteenth of August.”

“She is stopping on, too.”

“Mrs. Chepstow!  In the dog-days!”

“She doesn’t seem to have anywhere special to go to.”

“Oh!”

Isaacson opened a book, and laid his hand upon a page.  It happened to be a book on poisons and their treatment.  He smoothed the page down mechanically and kept his hand there.

“I say, Isaacson, you couldn’t have the blood-lust?”

“I hope not.  I think not.”

“I believe you hate it as I do, hate and loathe it with all your soul.  But I’ve always felt that you think for yourself, and don’t care a rap what the world is thinking.  I’ve looked in to-night to say good-bye, and to ask you, if you can get the time, just to give an eye to—­to Mrs. Chepstow now and again.  I know she would value a visit from you, and she really is infernally lonely.  If you go, she won’t bore you.  She’s a clever woman, and cares for things you care for.  Will you look in on her now and then?”

Isaacson lifted his hand from the book.

“I will call upon her,” he said.

“Good!”

“But are you sure she wishes it?”

“Quite sure—­for she told me so.”

The simplicity of this answer made Isaacson’s mind smile and something else in him sigh.

“I have to go into the country,” Nigel said.  “I’ve got to see Harwich and Zoe, my sister-in-law you know, and my married sister—­”

A sudden look of distress came into his eyes.  He got up.  The look of distress persisted.

“Good-night, Isaacson, old fellow!”

He grasped the Doctor’s hand firmly, and his hand was warm and strong.

“Good-night.  I like to feel I know one man who thinks so entirely for himself as you do.  For—­I know you do.  Good-bye.”

The look of distress had vanished, and his sincere eyes seemed to shine again with courage and with strength.

“Good-bye.”

When he was gone, Isaacson stood by the mantel-piece for nearly five minutes, thinking and motionless.  The sound of the little clock striking roused him.  He lifted his head, looked around him, and was just going to switch off the light, when he noticed the open book on his table.  He went to shut it up.