'The very next morning she was found to be missing from her room. A note was left addressed to the coroner. It ran as follows:

'I tried to speak to the vicar yesterday, to confess all, but was not allowed. She would not let me. I can make amends only one way - a life for a life; and my life must go the same way as hers did. I, too, must drown in the deep sea. I believed I was justified. I see now that that was not so. If I desire Amy's forgiveness I must go to her. Let no one be blamed for my death -

Mary Barton

'Her clothes were found lying on the beach in a secluded cove nearby, and it seemed clear that she had undressed there and swum resolutely out to sea where the current was known to be dangerous, sweeping one down the coast.

'The body was not recovered, but after a time leave was given to presume death. She was a rich woman, her estate being proved at a hundred thousand pounds. Since she died intestate it all went to her next of kin - a family of cousins in Australia. The papers made discreet references to the tragedy in the Canary Islands, putting forward the theory that the death of Miss Durrant had unhinged her friend's brain. At the inquest the usual verdict of Suicide whilst temporarily insane was returned.

'And so the curtain falls on the tragedy of Amy Durrant and Mary Barton.'

There was a long pause and then Jane Helier gave a great gasp.

'Oh, but you mustn't stop there - just at the most interesting part Go on.'

'But you see, Miss Helier, this isn't a serial story. This is real life; and real life stops just where it chooses.'

'But I don't want it to,' said Jane. 'I want to know.'

'This is where we use our brains, Miss Helier,' explained Sir Henry. 'Why did Mary Barton kill her companion? That's the problem Dr Lloyd has set us.'

'Oh, well,' said Miss Helier, 'she might have killed her for lots of reasons. I mean - oh, I don't know. She might have got on her nerves, or else she got jealous, although Dr Lloyd doesn't mention any men, but still on the boat out - well, you know what everyone says about boats and sea voyages.'

Miss Helier paused, slightly out of breath, and it was borne in upon her audience that the outside of Jane's charming head was distinctly superior to the inside.

'I would like to have a lot of guesses,' said Mrs Bantry. 'But I suppose I must confine myself to one. Well, I think that Miss Barton's father made all his money out of ruining Amy Durrant's father, so Amy determined to have her revenge. Oh, no, that's the wrong way round. How tiresome! Why does the rich employer kill the humble companion? I've got it Miss Barton had a young brother who shot himself for love of Amy Durrant. Miss Barton waits her time. Amy comes down in the world. Miss B. engages her as companion and takes her to the Canaries and accomplishes her revenge. How's that?'

'Excellent,' said Sir Henry. 'Only we don't know that Miss Barton ever had a young brother.'

'We deduce that,' said Mrs Bantry. 'Unless she had a young brother there's no motive. So she must have had a young brother. Do you see, Watson?'

'That's all very fine, Dolly,' said her husband. 'But it's only a guess.'

'Of course it is,' said Mrs Bantry. 'That's all we can do - guess. We haven't got any clues. Go on, dear, have a guess yourself.'

'Upon my word, I don't know what to say. But I think there's something in Miss Heller's suggestion that they fell out about a man. Look here, Dolly, it was probably some high church parson. They both embroidered him a cope or something, and he wore the Durrant woman's first. Depend upon it, it was something like that. Look how she went off to a parson at the end. These women all lose their heads over a good-looking clergyman. You hear of it over and over again.'

'I think I must try to make my explanation a little more subtle,' said Sir Henry, 'though I admit it's only a guess. I suggest that Miss Barton was always mentally unhinged. There are more cases like that than you would imagine. Her mania grew stronger and she began to believe it her duty to rid the world of certain persons - possibly what is termed unfortunate females. Nothing much is known about Miss Durrant's past. So very possibly she had a past - an "unfortunate" one. Miss Barton learns of this and decides on extermination. Later, the righteousness of her act begins to trouble her and she is overcome by remorse. Her end shows her to be completely unhinged. Now, do say you agree with me, Miss Marple.'

'I'm afraid I don't, Sir Henry,' said Miss Marple, smiling apologetically. 'I think her end shows her to have been a very clever and resourceful woman.'

Jane Helier interrupted with a little scream.

'Oh! I've been so stupid. May I guess again? Of course it must have been that Blackmail! The companion woman was blackmailing her. Only I don't see why Miss Marple says it was clever of her to kill herself. I can't see that at all.'

'Ah!' said Sir Henry. 'You see, Miss Marple knew a case just like it in St Mary Mead.'

'You always laugh at me, Sir Henry,' said Miss Marple reproachfully. 'I must confess it does remind me, just a little, of old Mrs Trout. She drew the old age pension, you know, for three old women who were dead, in different parishes.'

'It sounds a most complicated and resourceful crime,' said Sir Henry. 'But it doesn't seem to me to throw any light upon our present problem.'

'Of course not,' said Miss Marple. 'It wouldn't - to you. But some of the families were very poor, and the old age pension was a great boon to the children. I know it's difficult for anyone outside to understand. But what I really meant was that the whole thing hinged upon one old woman being so like any other old woman.'

'Eh?' said Sir Henry, mystified.

'I always explain things so badly. What I mean is that when Dr Lloyd described the two ladies first, he didn't know which was which, and I don't suppose anyone else in the hotel did. They would have, of course, after a day or so, but the very next day one of the two was drowned, and if the one who was left said she was Miss Barton, I don't suppose it would ever occur to anyone that she mightn't be.'

'You think - Oh! I see,' said Sir Henry slowly.

'It's the only natural way of thinking of it. Dear Mrs Bantry began that way just now. Why should the rich employer kill the humble companion? It's so much more likely to be the other way about I mean - that's the way things happen.'

'Is it?' said Sir Henry. 'You shock me.'

'But of course,' went on Miss Marple, 'she would have to wear Miss Barton's clothes, and they would probably be a little tight on her, so that her general appearance would look as though she had got a little fatter. That's why I asked that question. A gentleman would be sure to think it was the lady who had got fatter, and not the clothes that had got smaller - though that isn't quite the right way of putting it'

'But if Amy Durrant killed Miss Barton, what did she gain by it?' asked Mrs Bantry. 'She couldn't keep up the deception for ever.'

'She only kept it up for another month or so,' pointed out Miss Marple. 'And during that time I expect she travelled, keeping away from anyone who might know her. That's what I meant by saying that one lady of a certain age looks so like another. I don't suppose the different photograph on her passport was ever noticed - you know what passports are. And then in March, she went down to this Cornish place and began to act queerly and draw attention to herself so that when people found her clothes on the beach and read her last letter they shouldn't think of the commonsense conclusion.'

'Which was?' asked Sir Henry.

'No body,' said Miss Marple firmly. 'That's the thing that would stare you in the face, if there weren't such a lot of red herrings to draw you off the trail - including the suggestion of foul play and remorse. No body. That was the real significant fact'