His answer was curt and incisive.

"Do you mean to tell me," Mary said, "that, after you left me and went down the corridor towards the library, you neither went in to Hartley nor spoke to him!"

"I do!"

"Then how do you account for the fact that, almost immediately after you had crossed Bude in the hall, he heard the sound of voices in the library?"

Robin Greve stood up abruptly.

"Bude, you say, makes this statement?"

"Certainly!"

"To whom, may I ask?"

He spoke sharply and there was a challenging ring in his voice. It nettled the girl.

"Only to me," she said quickly, and added: "You needn't think he has told the police!"

Very deliberately Robin plucked his handkerchief from his sleeve, wiped his lips, and replaced it. The girl saw that his hands were trembling.

"Why do you say that to me?" he demanded rather fiercely.

Mary Trevert shrugged her shoulders.

"This afternoon," she said, "when I told you of my engagement to Hartley, you began by abusing him to me, you rushed from the room making straight for the library where we all know that Hartley was working, and a few minutes after Bude hears voices raised in anger proceeding from there. The next thing we know is that Hartley has ..."

She broke off and looked away.

"Mary,"--Robin's voice was grave, and he had mastered all signs of irritation,--"you and I have known one another all our lives. You ought to know me well enough by now to understand that I don't tell you lies.

When I say I haven't seen or spoken to Hartley Parrish since lunch this afternoon, that is the truth!"

"How can it be the truth?" the girl insisted. "Horace and Dr. Romain were both in the lounge-hall, Bude was in the hall, the other menservants were in the servants' hall. You are the only man in the house not accounted for, and a minute before Bude heard these voices you go down the corridor towards the library. I can understand you wanting to keep it from the police, but why do you want to deceive _me_?"

"Mary," answered the young man sternly, "I know you're upset, but that's no justification for persisting in this stupid charge against me. I tell you I never saw Parrish or spoke to him, either, between lunch and when I saw him lying dead in the library. I am not going to repeat the denial. But you may as well understand now that I am not in the habit of allowing my friends to doubt my word!"

Mary flamed up at his tone.

"If you are my friend," she cried, "why can't you trust me? Why should I find this out from Bude? Why should I be humiliated by hearing from the butler that he kept this evidence from the police in order to please me because you and I are friends? I am only trying to help you, to shield you ..."

"That will do, Mary," he said. "No, you must hear what I have to say. If you insist on disbelieving me, you must. But I don't want you to help me. I don't want you to shield me. I shall make it my business to see that Bude's evidence is brought before the detective inspector from Scotland Yard who is being brought down here to handle the case ..."

"A detective from Scotland Yard?" the girl repeated.

"Yes, a detective. Humphries is puzzled by several points about this case and has asked for a.s.sistance from London. He is right. Neither the circ.u.mstances of Parrish's death nor the motive of his act are clear.

Bude's evidence is sufficient proof that somebody did gain access to the library this afternoon. In that case...."

"Yes...."

"In that case," said Greve slowly, "it may not be suicide...."

Mary put one hand suddenly to her face as women do when they are frightened. She shrank back.

"You mean...."

He nodded.

"Murder!"

The girl gave a little gasp. Then she stretched out her hand and touched his arm.

"But, Robin," she spoke in quick gasps,--"you can't give the police this evidence of Bude's. Don't you see it incriminates _you?_ Don't you realize that every sc.r.a.p of evidence points to you as being the man that visited Mr. Parrish in the library this afternoon? You're a lawyer, Robin. You understand these things. Don't you see what I mean?"

He nodded curtly.

"Perfectly," he replied coldly.

"Bude will do what I tell him," the girl hurried on. "There is no need for the police to know...."

"On the contrary," said the other imperturbably, "it is essential they should be told at once."

The girl grasped the lapels of his coat in her two hands. Her breath came quickly and she trembled all over.

"Are you mad, Robin?" she cried. "Who could have wanted to kill poor Hartley? Why should you put these ideas into the heads of the police?

Bude may have imagined everything. Now, you'll be sensible, promise me...."

Very gently he detached the two slim hands that held his coat. His mouth was set in a firm line.

"We are going to sift this thing to the bottom, Mary," he said, "no matter what are the consequences. You owe it to Parrish and you owe it to me...."

The telephone trilled suddenly.

Robin picked up the receiver,

"Yes, Bude," he said.

There was a moment's silence in the room broken as the clock on the mantelpiece chimed nine times. Then Robin said into the telephone:

"Right! Tell him I'll be down immediately!"

He put down the receiver and turned to Mary.

"A detective inspector has arrived from London. He is asking to see me.

I must go downstairs."

Mary, her elbows on the mantelpiece, was staring into the fire. At the sound of his voice she swung round quickly.

"Robin!" she cried.