“But the fact that Kemp knew how Sir Horace was dressed doesn’t prove that he saw Sir Horace after Holymead left the house,” said Rolfe.  “Kemp may have seen Sir Horace before Holymead arrived.”

“Quite true, Rolfe,” said Crewe.  “I haven’t lost sight of that point.  I think you will agree with me that there is a bit of a mystery here which wants clearing up.”

They drove back to town, and, in accordance with the arrangement Crewe had made with Mr. Walters before leaving the court, they waited on that gentleman at his chambers in Lincoln’s Inn.  There Crewe told him of the result of their investigations at Riversbrook.  Mr. Walters was professionally pleased at the prospect of destroying the evidence of Kemp.  He was not a hard-hearted man, and personally he would have preferred to see Holymead acquitted, if that were possible, but as the prosecuting Counsel he felt a professional satisfaction in being placed in the position to expose perjured evidence.

“Excellent! excellent!” he exclaimed, rubbing his hands with gratification as he spoke.  “Knowing what we know now, it will be a comparatively easy task to expose the witness Kemp under cross-examination, and show his evidence to be false.”  Mr. Walters looked as though he relished the prospect.

It was arranged that Inspector Chippenfield should be called to give evidence in rebuttal as to the impossibility of seeing the library window through the tree, and that an arboriculturist should also be called.  Mr. Walters agreed to have the expert in attendance at the court in the morning.

But Crewe had something more on his mind, and he waited until Chippenfield and Rolfe had taken their departure in order to put his views before the prosecuting counsel.  Then he pointed out to him that to prove that Kemp’s evidence was false was merely to obtain a negative result.  What he wanted was a positive result.  In other words, he wanted Kemp’s true story.

“You do not think, then, that Kemp is merely committing perjury in order to get Holymead off?” asked Walters meditatively.  “You think he is hiding something?”

Crewe replied, with his faint, inscrutable smile, that he had no doubt whatever that such was the case.  He thought Kemp’s true story might be obtained if Walters directed his cross-examination to obtaining the truth instead of merely to exposing falsehood.  It was evident to him that Kemp had come forward in order to save the prisoner.  How far was he prepared to go in carrying out that object?  When he was made to realise that his perjury, instead of helping Holymead, had helped to convince the jury of the prisoner’s guilt, would he tell the true story of how much he knew?

“My own opinion is that he will,” continued Crewe.  “I studied his face very closely while he was in the box to-day, and I am convinced he would go far—­even to telling the truth—­in order to save the only man who was ever kind to him.”