I cannot pretend that there was anything sinister in the atmosphere that evening. Nothing of the sort that is supposed to precede a crime. Nobody walked about looking furtive, no whispered quarrels were interrupted, no mysterious strangers lurked near the house. Although afterwards, as you may imagine, I went over the events of the day again and again in my mind, I could remember nothing which might have served as a warning, nothing at all extraordinary in anyone's behaviour. That is why the thing came as such an abominable shock to me.

I remember, of course — I have good cause to remember — that we discussed crime over our cocktails. But we discussed it in general terms, and how could one have guessed that there was any relevance in the discussion? And I could not say for certain who had brought up the subject. Perhaps if I could have done so, if anyone could have done so, it would have helped us later to understand. For that discussion was relevant, appallingly relevant, in a very special sense. As you shall see.

But at the time — well, at the Thurstons' week-end parties, crime might be discussed, or religion, politics, the cinema, or ghosts. Any topic of general interest which arose was sure to be pretty well threshed out. That was the kind of party which the Thurstons gave, a party at which everyone talked a great deal, shouting opinions which he would afterwards have denied, and trying to shout them as cleverly as possible. I do not mean that it was all rather self-conscious and arty, like those awful parties in London at which women with unpleasant breath advocate free love and nudism. But at the Thurstons' conversation was enjoyed, and not treated as a tiresome stop-gap between dinner and bridge.

Dr. Thurston himself was no conversationalist, though he enjoyed listening, and could put in an incentive phrase now and again. He was a big, bespectacled man, rather Teutonic in appearance, and in manner, too, for he showed a jolly German simplicity and sentimentality to everyone. He liked pressing his guests to food and drink and cigars, with booming emphasis. He had been the local doctor in that Sussex village, till he married, and although he no longer practised he had kept on the house, because he liked it, and allowed the new practitioner to build afresh. It was understood that Mrs. Thurston had money; at all events they had been very well off since their marriage, and entertained a great deal.

She, too, was amiable, most amiable, but not very intelligent. Although I stayed with the Thurstons many times, and must have spent hours in the same room with Mary Thurston, I cannot recall a single sentence that she uttered. She was stout, and spent a great deal of money on her clothes, a big, blonde, rather painted woman, easy-going and quite unpretentious. I can see her clearly enough, even if I cannot remember words of hers, beaming round on us all, filling quite a wide arm-chair, giggling like a girl at flattery, obviously overflowing with kindness. 'The Goddess of Plenty' someone once called her, aptly enough, for as a hostess, from the practical point of view, she was supreme. The food was really exquisite, the house beautifully kept, and Mrs. Thurston had that important gift — a memory for drinks. She was a good woman.

Whoever may have started discussing crime, it was Alec Norris who did most of the talking, though he pretended to be contemptuous of the topic.

"Crime?" he said. "Can't we talk about anything else? Don't we get enough of it in books and films? I'm sick to death of this crime crime, crime, wherever you turn."

Dr. Thurston chuckled. He knew Norris, and knew why he spoke so bitterly. Norris was an unsuccessful writer of novels very different from murder mysteries — rather intense psychological books, with a good deal of sex in them. Dr. Thurston saw his chance of making Norris excited.

"But is it crime in those books?" he asked. "Crime as it really happens?"

Norris might have been a diver on a spring-board. He hesitated for one moment, blinking at Thurston, then he plunged. "No, I'm damned if it is,',' he said. "Literary crime is all baffling mystery and startling clues. Whereas in real life, murder, for instance, nearly always turns out to be some sordid business of a strangled servant girl. There are only two kinds of murder which could baffle the police for one second. One is that committed by a man with a victim who cannot be missed — like the recent Brighton murder. The other is the act of a madman, who murders for the sake of murder, without another motive. No premeditated murder could puzzle the police for very long; Where there's a motive and the victim's identified, there's an arrest."

He paused to swallow the rest of his cocktail. I was watching him, thinking what an odd-looking fellow Alec Norris was — narrow in head and body, with a bony face in which jaw and teeth, cheek-bones and forehead protruded, while the flesh seemed to have shrunk till it barely covered the skull.

Another guest spoke then. Young David Strickland, I think it was. "But an arrest doesn't always mean a verdict of guilty," he said. "There have been murderers so desperate that though they knew beforehand they would be suspected and probably charged, they took the chance. They were clever enough not to provide enough evidence."

I did not look with much interest towards Strickland, for I knew him quite well. He was younger than any of us, a thick-set fellow, fond of sport, particularly of racing. He was apt to try to borrow a fiver from you, but bore no malice if it was refused. He was some sort of protege of the Thurstons, and Dr. Thurston sometimes spoke to his wife of him good-humouredly as 'your lover, my dear'. There was nothing in that, however, though I could imagine Mary Thurston helping him out of difficulties. Nothing of the gigolo about young Strickland, a hard-drinking, gambling type, fond of smutty stories.

Alec Norris brushed aside his interruption. "The police will find the evidence, when they know their man," he said, and returned to his condemnation of detective fiction. "It's all so artificial," he said. "So unrelated to life. You, all of you, know these literary murders. Suddenly, in the middle of a party — like this one, perhaps — someone is found dead in the adjoining room. By the trickery of the novelist all the guests and half the staff are suspect. Then down comes the wonderful detective, who neatly proves that it was in fact the only person you never suspected at all. Curtain."

"Have another drink, Alec?"

"Thanks. But I haven't finished yet. I was going to point out that it has become a mere game — fox and hounds between readers and novelist. Only readers are getting clever nowadays. They don't suspect the obvious people, as they used to. But if the novelist has a character who wasn't at all the sort of person to have done it, they may just wonder, by analogy. Every one of the minor characters has been used. It has turned out to be the family lawyer, like you, Mr. Williams. The host himself, like you, Thurston. The young friend staying in the house, like you, Townsend," he glanced in my direction, "or like you, Strickland, or like me. The butler, like Stall, the Vicar, like Mr. Rider, the housemaid, like Enid, the chauffeur, like yours — what is his name? — or the very hostess, like you, Mrs. Thurston. Or else it has been a total stranger who doesn't appear till Chapter...