“But he can be stopped at the frontier!”

“Do you think Corbario is the man to let himself be trapped easily if he knows that he is pursued?” asked Kalmon incredulously.  “I do not.”

He rose from his chair and began to walk up and down, his hands behind him and his head bent.

Marcello paid no attention to him and was silent for a long time, sitting quite motionless and scarcely seeming to breathe.  What he felt he never could have told afterwards; he only knew that he suffered in every fibre of his brain and body, with every nerve of his heart and in every secret recess of his soul.  His mother seemed to have been dead so long, beyond the break in his memory.  The dreadful truth he had just heard made her die again before his eyes, by the hand of the man whom he and she had trusted.

“Kalmon,” he said at last, and the Professor stopped short in his walk.  “Kalmon, do you think she knows?”

It was like the cry of a child, but it came from a man who was already strong.  Kalmon could only shake his head gravely; he could find nothing to say in answer to such a question, and yet he was too human and kind and simple-hearted not to understand the words that rose to Marcello’s lips.

“Then she was happy to the end—­then she still believes in him.”

Kalmon turned his clear eyes thoughtfully towards Marcello’s face.

“She is gone,” he answered.  “She knows the great secret now.  The rest is nothing to the dead.  But we are living and it is much to us.  The man must be brought to justice, and you must help me to bring him down, if we have to hunt him round the world.”

“By God, I will!” said Marcello, in the tone of one who takes a solemn obligation.

He rose and stood upright, as if he were ready, and though he was still pale there was no look of weak horror left in his face, nor any weakness at all.

“Good!” exclaimed Kalmon.  “I would rather see you so.  Now listen to me, and collect your thoughts, Marcello.  Ercole is in Rome.  You remember Ercole, your keeper at the cottage by the shore?  Yes.  I got the last link in the evidence about Corbario’s attack on you from him to-day.  He is a strange fellow.  He has known it since last summer and has kept it to himself.  But he is one of those diabolically clever peasants that one meets in the Campagna, and he must have his reasons.  I told him to sleep at my house to-night, and when I went home he was sitting up in the entry with his dog.  I have sent him to the station to find out whether Corbario really left or not.  You don’t think he will succeed?  I tell you there are few detectives to be compared with one of those fellows when they are on the track of a man they hate.  I told him to come here, no matter how late it might be, since he is your man.  I suppose he can get in?”

“Of course.  There is a night-bell for the porter.  Ercole knows that.  Besides, the porter will not go to bed as long as you are here.  While we are waiting for him, tell me what Ercole has found out.”