‘Sellon doesn’t look like a murderer.’

‘They very often don’t, you know. He didn’t look, either, like the sort of man who would tell me a thundering great lie, except for a very good reason. But people do tell lies when they’re frightened.’

‘I suppose he didn’t notice till after he’d said that about the clock that it implied having been inside the house.’

‘No. You’ve got to be a very sharp-witted person to see ahead when you’re telling half-truths. A story that’s a lie from beginning to end will be consistent. And since he obviously hadn’t meant to tell the story of the quarrel at all, he had to make up his mind on the spur of the moment. The thing that’s bothering me is, how did Sellon get into the house?’

Noakes must have let him in.’

‘Just so. Here’s an elderly man, locked up alone in a house. Up comes a young man, big and strong and in a murderous rage, and quarrels with him, using strong language and possibly threats. The old man tells him to be off, and bangs the window shut. The young man goes on knocking at the doors and trying to get in. The old man has nothing to gain by admitting him; yet be does it, and obligingly turns his back to him, on purpose that the angry young man may attack him with a blunt instrument. It is possible, but, as Aristotle might say, it is an improbable-possible.’

‘Suppose Sellon said he had got the money after all, and Noakes let him in and sat down to write a-no, he wouldn’t write a receipt, of course. Nothing on paper. Unless Sellon threatened him.’

‘If Sellon had the money, Noakes could have told him to hand it in through the window.’

‘Well, suppose he did hand it in-or said he was going to. Then, when Noakes opened the window, Sellon could have climbed in himself. Or could he? Those mullions are pretty narrow.’

‘You can have no idea,’ said Peter, irrelevantly, ‘how refreshing it is to talk to somebody who has a grasp of method.

The police are excellent fellows, but the only principle of detection they have really grasped is that wretched phrase, Cui bono. They will hare off after motive, which is a matter for psychologists. Juries are just the same. If they can see a motive they tend to convict, however often the judge may tell them that there’s no need to prove motive, and that motive by itself will never make a case. You’ve got to show how the thing was done, and then, if you like, bring in motive to back up your proof. If a thing could only have been done one way, and if only one person could have done it that way, then you’ve got your criminal, motive or no motive. There’s How, When, Where, Why and Who-and when you’ve got How. you’ve got Who. Thus spake Zarathustra.’

‘I seem to have married my only intelligent reader. That’s the way you construct it from the other end, of course. Artistically, it’s absolutely right.’

‘I have noticed that what’s right in art is usually right in practice. In fact, nature is a confirmed plagiarist of art, as somebody has observed. Go on with your theory-only do remember that to guess how a job might have been done isn’t the same thing as proving that it was done that way. If you will allow me to say so, that is a distinction which people of your profession are very liable to overlook. They will confuse moral certainty with legal proof.’

‘

‘I shall throw something at you in a minute… I say, do you think something might have been thrown at Noakes?

Through the window? Bother! Now I’ve got two theories at once. No-wait!… Sellon gets Noakes to open the window and then starts to climb in. You didn’t answer about those mullions.’

‘I think I could climb in through them; but then I’m rather narrow in the shoulders compared with Sellon. But on the principle that where your head can go your body can follow I dare say he could manage it. Not very quickly, and not without giving Noakes plenty of warning of his intentions.’

‘That’s where the throwing comes in. Suppose Sellon started to climb and Noakes got alarmed and made for the door. Then Sellon might snatch up something.’

‘What?’

‘That’s true. He would scarcely have brought a stone or anything on purpose. He might have picked one up in the garden before he came back to the window. Or-I know!

That paper-weight on the sill. He could have snatched that up, and chucked it at Noakes’s retreating back. Would that work? I’m not good at trajectories and things.’

‘Very likely it would. I’d have to go and look.’

‘Well then. Oh, yes. Then he’d only have to finish scrambling in, pick up the paper-weight and put it back and go out through the window again.’

‘Really?’

‘Of course not; it was locked inside. No. He’d shut and lock the window, get Noakes’s keys from his pocket, open the front door, put back the keys and-well, then he’d have to go out leaving the door unlocked. And when Noakes came to, he obligingly locked it behind him. We’ve got to allow for that possibility, whoever did the murder.’

‘That’s really brilliant, Harriet. It’s very difficult to find a flaw in it. And I’ll tell you another thing. Sellon was the only person who could, with comparative safety, leave the door unlocked. In fact, it would be an advantage.’

‘You’ve got ahead of me there. Why?’

‘Why, because he was the village policeman. Look what happens next. In the middle of the night, he takes it into his head to go on a round of inspection. His attention, as he would put it in his report, is directed to the house by the circumstances of the candles being still alight in the sittingroom. That’s why he left them burning, which no other murderer would be likely to do. He tries the door and finds it open. He goes in, sees that everything looks nice and natural, and then hurries out to call up the neighbours with the announcement that some tramp or other has been in and knocked Mr Noakes on the head. It’s a nuisance to be the last man to see the deceased alive, but it’s a hell of a good wheeze to be the first to discover the body. It must have been a nasty shock to find that door locked after all.’

‘Yes. I suppose that would make him give up his idea. Especially if he looked in through the window and saw that Noakes wasn’t lying where he’d left him. The curtains weren’t drawn, were they? No-I remember-they were open when we arrived. What would he think?’

‘He’d think Noakes wasn’t killed after all, and would wait for the morning, wondering when-and how-’

‘Poor man!-And then, when nothing happened after all, and Noakes didn’t turn up-why, it was enough to drive him dotty.’

‘If it happened that way.’

‘And then we came and-I suppose he was hanging about here all morning, waiting to hear the worst. He was right on the spot when the body was found, wasn’t he?… I say, Peter, all this is a bit grim.’

‘It’s only a theory, after all. We haven’t proved a word of it. That’s the worst of you mystery-mongers. Anything’s a solution so long as it holds together. Let’s make a theory about somebody else. Whom shall we have? How about Mrs Ruddle? She’s a tough old lady and not an altogether sympathetic character.’

‘Why on earth should Mrs Ruddle-?’

‘Never mind. Why. Why never gets you anywhere. Mrs Ruddle came to borrow a drop of paraffin. Noakes was sniffing round and heard her. He invited her to step in and explain herself. He said he had often had doubts of her honesty. She said he owed her a week’s money. High words passed. He made for her. She snatched up the poker. He ran away and she threw the poker at him and caught him on the back of the head. That’s Why enough, when people lose their tempers. Unless you prefer to believe that Noakes made improper advances to Mrs Ruddle and she dotted him one accordingly.’

Idiot!’

‘Well. I don’t know. Look at old James Fleming and Jessie MacPherson. I shouldn’t fancy Mrs Ruddle myself, but then, my standard is high. Very well. Mrs Ruddle knocks Noakes on the head, and-wait a minute; this is coming rather pretty. She runs over to the cottage in a terrible stew, crying, “Bert! Bert! I’ve killed Mr Noakes!” Bert says, “Oh, nonsense,” and they come back to the house together, just in time to see Noakes go tumbling down the cellar steps. Bert goes down-’