'Miss Barton had had two references with her. One she had forgotten, the other name she recollected after an effort. It proved to be that of a lady who was now abroad, having gone to Australia. She was written to. Her answer, of course, was a long time in coming, and I may say that when it did arrive there was no particular help to be gained from it. She said Miss Durrant had been with her as companion and had been most efficient and that she was a very charming woman, but that she knew nothing other private affairs or relations.

'So there it was - as I say, nothing unusual, really. It was just the two things together that aroused my uneasiness. This Amy Durrant of whom no one knew anything, and the Spanish woman's queer story. Yes, and I'll add a third thing: When I was first bending over the body and Miss Barton was walking away towards the huts, she looked back. Looked back with an expression on her face that I can only describe as one of poignant anxiety - a kind of anguished uncertainty that imprinted itself on my brain.

'It didn't strike me as anything unusual at the time. I put it down to her terrible distress over her friend. But, you see, later I realized that they weren't on those terms. There was no devoted attachment between them, no terrible grief. Miss Barton was fond of Amy Durrant and shocked by her death - that was all.

'But, then, why that terrible poignant anxiety? That was the question that kept coming back to me. I had not been mistaken in that look. And almost against my will, an answer began to shape itself in my mind. Supposing the Spanish woman's story were true; supposing that Mary Barton wilfully and in cold blood tried to drown Amy Durrant. She succeeds in holding her under water whilst pretending to be saving her. She is rescued by a boat. They are on a lonely beach far from anywhere. And then I appear - the last thing she expects. A doctor! And an English doctor! She knows well enough that people who have been under water far longer than Amy Durrant have been revived by artificial respiration. But she has to play her part - to go off leaving me alone with her victim. And as she turns for one last look, a terrible poignant anxiety shows in her face. Will Amy Durrant come back to life and tell what she knows?'

'Oh!' said Jane Helier. 'I'm thrilled now.'

'Viewed in that aspect the whole business seemed more sinister, and the personality of Amy Durrant became more mysterious. Who was Amy Durrant? Why should she, an insignificant paid companion, be murdered by her employer? What story lay behind that fatal bathing expedition? She had entered Mary Barton's employment only a few months before. Mary Barton had brought her abroad, and the very day after they landed the tragedy had occurred. And they were both nice, commonplace, refined Englishwomen! The whole thing was fantastic, and I told myself so. I had been letting my imagination run away with me.'

'You didn't do anything, then?' asked Miss Helier.

'My dear young lady, what could I do? There was no evidence. The majority of the eye-witnesses told the same story as Miss Barton. I had built up my own suspicions out of a fleeting expression which I might possibly have imagined. The only thing I could and did do was to see that the widest inquiries were made for the relations of Amy Durrant The next time I was in England I even went and saw the landlady of her room, with the results I have told you.'

'But you felt there was something wrong,' said Miss Marple.

Dr Lloyd nodded.

'Half the time I was ashamed of myself for thinking so. Who was I to go suspecting this nice, pleasant-mannered English lady of a foul and cold-blooded crime? I did my best to be as cordial as possible to her during the short time she stayed on the island. I helped her with the Spanish authorities. I did everything I could do as an Englishman to help a compatriot in a foreign country; and yet I am convinced that she knew I suspected and disliked her.'

'How long did she stay out there?' asked Miss Marple.

'I think it was about a fortnight. Miss Durrant was buried there, and it must have been about ten days later when she took a boat back to England. The shock had upset her so much that she felt she couldn't spend the winter there as she had planned. That's what she said.'

'Did it seem to have upset her?' asked Miss Marple.

The doctor hesitated.

'Well, I don't know that it affected her appearance at all,' he said cautiously.

'She didn't, for instance, grow fatter?' asked Miss Marple.

'Do you know - it's a curious thing your saying that. Now I come to think back, I believe you're right. She - yes, she did seem, if anything, to be putting on weight'

'How horrible,' said Jane Helier with a shudder. 'It's like - it's like fattening on your victim's blood.'

'And yet, in another way, I may be doing her an injustice,' went on Dr Lloyd. 'She certainly said something before she left, which pointed in an entirely different direction. There may be, I think there are, consciences which work very slowly - which take some time to awaken to the enormity of the deed committed.

'It was the evening before her departure from the Canaries. She had asked me to go and see her, and had thanked me very warmly for all I had done to help her. I, of course, made light of the matter, said I had only done what was natural under the circumstances, and so on. There was a pause after that. and then she suddenly asked me a question.

'"Do you think," she asked, "that one is ever justified in taking the law into one's own hands?"

'I replied that that was rather a difficult question, but that on the whole, I thought not. The law was the law, and we had to abide by it.

'"Even when it is powerless?"

'"I don't quite understand."

'"It's difficult to explain; but one might do something that is considered definitely wrong - that is considered a crime, even, for a good and sufficient reason."

'I replied dryly that possibly several criminals had thought that in their time, and she shrank back.

'"But that's horrible," she murmured. "Horrible."

'And then with a change of tone she asked me to give her something to make her sleep. She had not been able to sleep properly since - she hesitated - since that terrible shock.

'"You're sure it is that? There is nothing worrying you? Nothing on your mind?"

'"On my mind? What should be on my mind?"

'She spoke fiercely and suspiciously.

'"Worry is a cause of sleeplessness sometimes,' I said lightly.

'She seemed to brood for a moment.

'"Do you mean worrying over the future, or worrying over the past, which can't be altered?"

'"Either."

'"Only it wouldn't be any good worrying over the past. You couldn't bring back - Oh! what's the use! One mustn't think. One must not think."

'I prescribed her a mild sleeping draught and made my adieu. As I went away I wondered not a little over the words she had spoken. "You couldn't bring back - " What? Or who?

'I think that last interview prepared me in a way for what was to come. I didn't expect it, of course, but when it happened, I wasn't surprised. Because, you see, Mary Barton struck me all along as a conscientious woman - not a weak sinner, but a woman with convictions, who would act up to them, and who would not relent as long as she still believed in them. I fancied that in the last conversation we had she was beginning to doubt her own convictions. I know her words suggested to me that she was feeling the first faint beginnings of that terrible soul-searcher - remorse.

'The thing happened in Cornwall, in a small watering-place, rather deserted at that season of the year. It must have been - let me see - late March. I read about it in the papers. A lady had been staying at a small hotel there - a Miss Barton. She had been very odd and peculiar in her manner. That had been noticed by all. At night she would walk up and down her room, muttering to herself, and not allowing the people on either side of her to sleep. She had called on the vicar one day and had told him that she had a communication of the gravest importance to make to him. She had, she said, committed a crime. Then, instead of proceeding, she had stood up abruptly and said she would call another day. The vicar put her down as being slightly mental, and did not take her self-accusation seriously.