Phillips’s head jerked up as though he had come suddenly face to face with a threatening obstacle. He did not speak for perhaps half a minute and then he said very softly:

“Do you enjoy reading other people’s private correspondence?”

“About as much as you enjoy glaring into a septic abdomen, I should think,” rejoined Alleyn. “It has a technical interest.”

“I suppose you’ve spoken to the butler?”

“Would you like to give me your own explanation of the business?”

“No,” said Phillips. “No.”

“Speaking unofficially — a thing I am far too prone to do — I am extremely sorry for you, Sir John.”

Phillips looked at him.

“Do you know, I think I believe you,” he said. “Is there anything else?”

“No, I’ve kept you quite long enough. Would it be an awful bore for everyone if I had a word with the nurses who attended the case?”

“I don’t think they can tell you very much further.”

“Probably not, but I think I ought to see them unless they are all heavily engaged in operations.”

“The theatre is not in use at the moment. The matron and the nurse who assists her — Nurse Banks — will be free.”

“Splendid. What about Sir Derek’s personal nurse and the other one from the theatre — Nurse Harden, wasn’t it?”

“I will find out,” said Phillips. “Do you mind waiting?”

“Not at all,” murmured Alleyn with an involuntary glance at the marble woman. “May I see them one by one — it will be less violently embarrassing for all of us?”

“You do not impress me,” rejoined Phillips, “as a person who suffers from shyness, but no doubt you would rather sleuth in secret. You shall see them one by one.”

“Thank you.”

Alleyn waited only a few minutes after Sir John left him and then the door reopened to admit Sister Marigold, in whose countenance gentility, curiosity and resentment were exquisitely reflected.

“How do you do, matron?” said Alleyn.

“Good afternoon,” said Sister Marigold.

“Won’t you sit down? Here? Or under the statue?”

“Thank you very much, I’m sure.” She sat with a rustle, and eyed the inspector guardedly.

“Perhaps Sir John has told you the report on the post-mortem?” Alleyn suggested.

“It’s terrible. Such a loss, as I say, to the country.”

“Unthinkable. One of the really strong men in the right party,” said Alleyn with low cunning.

“Just what I said when it happened.”

“Now look here, matron, will you take mercy on a wretched ignorant policeman and help me out of the awful fog I’m wallowing in? Here’s this man, perhaps the foremost statesman of his time, lying dead with a quarter of a grain of hyoscine inside him, and here am I, an abysmally incompetent layman, with the terrific task before me of finding out how it got there. What the devil am I to do about it, matron?”

He smiled very charmingly into her competent spectacles. Her very veil seemed to lose starch.

“Well, really,” said Sister Marigold, “I’m sure it’s all very trying for everybody.”

“Exactly. You yourself must have had a great shock.”

“Well, I did. Of course, in the ordinary way we nurses become accustomed to the sad side of things. People think us dreadfully hard-hearted sometimes.”

“You won’t get me to believe that. Of course, this discovery— ”

“That’s what makes it so dreadful, Mr. — er — I never could have believed it, never. Such a thing has never happened in the whole of my experience. And for it to be after an operation in my own theatre! Nobody could have taken more care. Nothing went wrong.”

“Now you’ve hit the nail right on the head!” exclaimed Alleyn, gazing at her as if she was a sort of sibyl. “I felt assured of that. You know as well as I do, matron, that Sir Derek was a man with many bitter enemies. I may tell you in confidence that at the Yard we know where to look. We are in close touch with the Secret Service”—he noted with satisfaction the glint of intrigue in her eye—“and we are pretty sure how the land lies. In our midst — in our very midst, matron — are secret agents, secret societies, powers of evil known to the Yard but unsuspected by the general public. Mercifully so.” He stopped short, folded his arms, and wondered how much of this the woman would swallow. Apparently the whole dose.

“Fancy!” breathed Sister Marigold. “Just fancy!”

“Well — that’s the position,” said Alleyn grandly, throwing himself back in his chair. “But here’s my difficulty. Before we can fire point-blank we’ve got to clear away the other possibilities. Suppose we made an arrest now — what would be the defense? An attempt would be made to throw suspicion on innocent persons, on the very people who fought to save Sir Derek’s life, on the surgeon who operated, and on his assistants.”

“But that’s terrible!”

“Nevertheless it is what would happen. Now to meet that position I must have the actual history of Sir Derek’s operation, in all its details, at my fingers’ ends. That is why I have laid my cards on the table, matron, and that is why I have come to you.”

Sister Marigold stared at him so long that he wondered nervously if he had been inartistic. However, when she did speak, it was with the greatest air of earnestness.

“I shall consider it my duty,” she said, “to give you what help I can.”

Alleyn thought it better not to shake hands with her. He merely said with quiet reverence:

“Thank you, matron, you have made a wise decision. Now to come down to tin tacks. I understand Sir John performed the operation, assisted by Mr. Thoms and with Dr. Roberts as anæsthetist. Sir John gave the hyoscine injection and prepared it himself.”

“Yes. Sir John always does that. As I always say, he’s so conscientious.”

“Splendid, isn’t it? And Mr. Thoms gave the anti-gas injection. Nurse Harden brought it to him, didn’t she?”

“Yes, she did. Poor Harden, she was dreadfully upset. Sir Derek was a great friend of her own family, a very old Dorsetshire family, Mr. — er— ”

“Really? Strange coincidence. She fainted afterwards, didn’t she, poor girl?”

“Yes. But I assure you she did her work all through the op., quite as usual — really.” Sister Marigold’s voice trailed away doubtfully.

“Someone said something about a delay over the anti-gas injection.”

“It was only for a moment. She told me afterwards she was so faint she had to pause before she brought it across.”

“Yes, I see. Frightful bad luck. Nurse Banks gave the camphor injection, didn’t she?”

“She did.” Sister Marigold’s thin lips closed in a whippy line.

“And prepared the serum?”

“That is so.”

“I suppose I’ll have to see her. Between you and me and the Marble Lady, matron, she rather alarms me.”

“H’m” said Sister Marigold. “Really? Fancy!”

“Still, it is my duty and I must. Is she on the premises?”

“Nurse Banks is leaving us to-morrow. I believe she is in the hospital this afternoon.”

“Leaving you, is she? Does she frighten you too, matron?”

Sister Marigold pursed up her lips.

“She is not a type I care to have nursing for me,” she said. “As I say, personal feelings should not interfere with a nurse’s work, much less political opinions.”

“I thought she looked as if she was suffering from High Ideals,” Alleyn remarked.

“Call them high ideals! Beastly Bolshevik nonsense,” said Sister Marigold vigorously. “She had the impertinence to tell me, in my own theatre, that she would be glad if the patient— ” She stopped short and looked extremely uncomfortable. “Not, of course, that she meant anything. Still, as I say— ”

“Yes, quite. They’d say anything, some of these people. Of course with those views she’d loathe the very sight of O’Callaghan.”

“How she dared!” fumed Sister Marigold.

“Tell me about it,” said Alleyn winningly.

After a little hesitation she did.