The Thirteen Problems by Agatha Christie

Mr and Mrs Denman that he ought to be in an institution, but Mrs Denman wouldn’t hear of it at any price.”
    ‘I will say for Mabel that she always had a kindly heart.
    ‘Well, there the thing was. I thought it over in every aspect, and at last I decided that there was only onething to be done. In view of the rumours that were going about, permission must be applied for to exhume the body, and a proper post-mortem must be made and lying tongues quietened once and for all. Mabel, of course, made a fuss, mostly on sentimental grounds—disturbing the dead man in his peaceful grave, etc., etc.—but I was firm.
    ‘I won’t make a long story of this part of it. We got the order and they did the autopsy, or whatever they call it, but the result was not so satisfactory as it might have been. There was no trace of arsenic—that was all to the good—but the actual words of the report were that there was nothing to show by what means deceased had come to his death .
    ‘So, you see, that didn’t lead us out of trouble altogether. People went on talking—about rare poisons impossible to detect, and rubbish of that sort. I had seen the pathologist who had done the post-mortem, and I had asked him several questions, though he tried his best to get out of answering most of them; but I got out of him that he considered it highly unlikely that the poisoned mushrooms were the cause of death. An idea was simmering in my mind, and I asked him what poison, if any, could have been employed to obtain that result. He made a long explanation to me, most of which, I must admit, I did not follow, but it amounted to this: Thatdeath might have been due to some strong vegetable alkaloid.
    ‘The idea I had was this: Supposing the taint of insanity was in Geoffrey Denman’s blood also, might he not have made away with himself? He had, at one period of his life, studied medicine, and he would have a good knowledge of poisons and their effects.
    ‘I didn’t think it sounded very likely, but it was the only thing I could think of. And I was nearly at my wits’ end, I can tell you. Now, I dare say you modern young people will laugh, but when I am in really bad trouble I always say a little prayer to myself—anywhere, when I am walking along the street, or at a bazaar. And I always get an answer. It may be some trifling thing, apparently quite unconnected with the subject, but there it is. I had that text pinned over my bed when I was a little girl: Ask and you shall receive . On the morning that I am telling you about, I was walking along the High Street, and I was praying hard. I shut my eyes, and when I opened them, what do you think was the first thing that I saw?’
    Five faces with varying degrees of interest were turned to Miss Marple. It may be safely assumed, however, that no one would have guessed the answer to the question right.
    ‘I saw,’ said Miss Marple impressively, ‘ the windowof the fishmonger’s shop . There was only one thing in it, a fresh haddock .’
    She looked round triumphantly.
    ‘Oh, my God!’ said Raymond West. ‘An answer to prayer—a fresh haddock!’
    ‘Yes, Raymond,’ said Miss Marple severely, ‘and there is no need to be profane about it. The hand of God is everywhere. The first thing I saw were the black spots—the marks of St Peter’s thumb. That is the legend, you know. St Peter’s thumb. And that brought things home to me. I needed faith, the ever true faith of St Peter. I connected the two things together, faith—and fish.’
    Sir Henry blew his nose rather hurriedly. Joyce bit her lip.
    ‘Now what did that bring to my mind? Of course, both the cook and house-parlourmaid mentioned fish as being one of the things spoken of by the dying man. I was convinced, absolutely convinced, that there was some solution of the mystery to be found in these words. I went home determined to get to the bottom of the matter.’
    She paused.
    ‘Has it ever occurred to you,’ the old lady went on, ‘how