beggar with all that evidence piled up against him mightn't have had such a break.'
Mary shivered again. 'Don't say that. I like to think the innocent are — protected.'
'Do you, my dear?' His voice was gentle.
Mary burst out suddenly: 'Thomas, I'm worried. I'm frightfully worried.'
'Yes.'
'It's about Mr. Treves.'
Thomas dropped his pipe on the stones. His voice changed as he bent to pick it up.
'What about Mr. Treves?'
'That night he was here — that story he told — about a little murderer! I've been wondering, Thomas … Was it just a story? Or did he tell it with a purpose?'
'You mean,' said Royde deliberately, 'was it aimed at someone who was in the room?'
Mary whispered, 'Yes.'
Thomas said quietly: 'I've been wondering, too. As a matter of fact, that was what I was thinking about when you came along just now.'
Mary half-closed her eyes.
'I've been trying to remember … He told it, you know, so very deliberately. He almost dragged it into the conversation. And he said he would recognise the person anywhere. He emphasised that. As though he had recognised him.'
'M'm,' said Thomas. 'I've been through all that.'
'But why should he do it? What was the point?'
'I suppose,' said Royde, 'it was a kind of warning. Not to try anything on.'
'You mean that Mr. Treves knew that Camilla was going to be murdered?'
'No-o. I think that's too fantastic. It may have been just a general warning.'
'What I've been wondering is, do you think we ought to tell the police?' To that Thomas again gave his thoughtful consideration.
'I think not,' he said at last. 'I don't see that it's relevant in any way. It's not as though Treves were alive and could tell them anything.'
'No,' said Mary. 'He's dead!' She gave a quick shiver. 'It's so odd, Thomas, the way he died.'
'Heart attack. He had a bad heart.'
'I mean that curious business about the lift being out of order. I don't like it.'
'I don't like it very much myself,' said Thomas Royde.
XI
Superintendent Battle looked round the bedroom. The bed had been made. Otherwise the room was unchanged. It had been neat when they first looked round it. It was neat now.
'That's it,' said Superintendent Battle, pointing to the old-fashioned steel fender. 'Do you see anything odd about that fender?'
'Must take some cleaning,' said Jim Leach. 'It's well kept. Nothing odd about it that I can see, except — yes, the left-hand knob is brighter than the right-hand one.'
'That's what put Hercule Poirot into my head,' said Battle . 'You know his fad about things not being quite symmetrical — gets him all worked up. I suppose I thought unconsciously, ‘That would worry old Poirot,' and then I began talking about him. Get your fingerprint kit, Jones, we'll have a look at those two knobs.'
Jones reported presently. 'There are prints on the right-hand knob, sir, none on the left.'
'It's the left one we want, then. Those other prints are the housemaid's when she last cleaned it. The left- hand one has been cleaned since.'
'There was a bit of screwed-up emery paper in this waste-paper basket,' volunteered Jones. 'I didn't think it meant anything.'
'Because you didn't know what you were looking for, then. Gently now, I'll bet anything you like that knob unscrews — yes, I thought so.'
Presently Jones held the knob up.
'It's a good weight,' he said, weighing it in his hands.
Leach, bending over it, said: 'There's something dark — on the screw.'
'Blood, as likely as not,' said Battle . 'Cleaned the knob itself and wiped it and that little stain on the screw wasn't noticed. I'll bet anything you like that's the weapon that caved the old lady's skull in. But there's more to find. It's up to you, Jones, to search the house again. This time, you'll know exactly what you're looking for.'
He gave a few swift detailed instructions. Going to the window he put his head out.
'There's something yellow tucked into the ivy. That may be another piece of the puzzle. I rather think it is.'
XII
Crossing the hall. Superintendent Battle was waylaid by Mary Aldin.
'Can I speak to you a minute. Superintendent?'
'Certainly, Miss Aldin. Shall we come in here?'
He threw open the dining-room door. Lunch had been cleared away by Hurstall.
'I want to ask you something, Superintendent. Surely you don't, you can't still think that this — this awful crime was done by one of us? It must have been someone from outside! Some maniac!'
'You may not be far wrong there. Miss Aldin. Maniac is a word that describes this criminal very well, if I'm not mistaken. But not an outsider.'
Her eyes opened very wide.
'Do you mean that someone in this house is — is mad?'
'You're thinking,' said the Superintendent, 'of someone foaming at the mouth and rolling their eyes. Mania isn't like that. Some of the most dangerous criminal lunatics have looked as sane as you or I. It's a question, usually, of having an obsession. One idea, preying on the mind, gradually distorting it. Pathetic, reasonable people who come up to you and explain how they're being persecuted and how everyone is spying on them — and you sometimes feel it must all be true.'
'I'm sure nobody here has any idea of being persecuted.'
'I only gave that as an instance. There are other forms of insanity. But I believe whoever committed this crime was under the domination of one fixed idea — an idea on which they had brooded until literally nothing else mattered or had any importance.'
Mary shivered. She said: 'There's something I think you ought to know.'
Concisely and clearly she told him of Mr. Treves' visit to dinner and of the story he had told. Superintendent Battle was deeply interested.
'He said he could recognise this person? Man or woman — by the way?'
'I took it that it was a boy the story was about — but it's true, Mr. Treves didn't actually say so — in fact, I remember now — he distinctly stated he would not give any particulars as to sex or age.'
'Did he? Rather significant, perhaps. And he said there was a definite physical peculiarity by which he could be sure of knowing this child anywhere?'
'Yes.'
'A scar, perhaps — has anybody here got a scar?'
He noticed the faint hesitation before Mary Aldin replied: 'Not that I have noticed.'
'Come now, Miss Aldin,' he smiled. 'You have noticed something. If so, don't you think that I shall be able to notice it, too?'
She shook her head.
'I — I haven't noticed anything of the kind.'
But he saw that she was startled and upset. His words had obviously suggested a very unpleasant train of thought to her. He wished he knew just what it was, but his experience made him aware that to press her at this minute would not yield any result.
