'Yes, Miss Marple, you've hit off my meaning exactly. Your charwoman person was lucky in the instance you relate. Her innocence was shown. But some people may go through a lifetime crushed by the weight of a suspicion that is really unjustified.'

'Are you thinking of some particular instance, Sir Henry?' asked Mrs. Bantry shrewdly.

'As a matter of fact, Mrs. Bantry, I am. A very curious case. A case where we believe murder to have been committed, but with no possible chance of ever proving it.'

'Poison, I suppose,' breathed Jane. 'Something untraceable:'

Dr. Lloyd moved restlessly and Sir Henry shook his head.

'No, dear lady. Not the secret arrow poison of the South American Indians! I wish it were something of that kind. We have to deal with something much more prosaic - so prosaic, in fact, that there is no hope of bringing the deed home to its perpetrator. An old gentleman who fell downstairs and broke his neck; one of those regrettable accidents which happen every day.'

'But what happened really?'

'Who can say? ' Sir Henry shrugged his shoulders. 'A push from behind? A piece of cotton or string tied across the top of the stairs and carefully removed afterward? That we shall never know.'

'But you do think that it - well, wasn't an accident? Now why? ' asked the doctor.

'That's rather a long story, but - well, yes, we're pretty sure. As I said, there's no chance of being able to bring the deed home to anyone - the evidence would be too flimsy. But there's the other aspect of the case - the one I was speaking about. You see, there were four people who might have done the trick. One's guilty, but the other three are innocent. And unless the truth is found out, those three are going to remain under the terrible shadow of doubt.'

'I think,' said Mrs. Bantry, 'that you'd better tell us your long story.'

'I needn't make it so very long after all,' said Sir Henry. 'I can at any rate condense the beginning. That deals with a German secret society - the Schivartze Hand - something after the lines of the Camorra or what is most people's idea of the Camorra. A scheme of blackmail and terrorisation. The thing started quite suddenly after the war and spread to an amazing extent.

Numberless people were victimised by it. The authorities were not successful in coping with it, for its secrets were jealously guarded, and it was almost impossible to find anyone who could be induced to betray them.

'Nothing much was ever known about it in England, but in Germany it was having a most paralysing effect. It was finally broken up and dispersed through the efforts of one man, a Dr. Rosen, who had at one time been very prominent in Secret Service work. He became a member, penetrated its inmost circle, and was, as I say, instrumental in bringing about its downfall.

'But he was, in consequence, a marked man, and it was deemed wise that he should leave Germany - at any rate for a time. He came to England, and we had letters about him from the police in Berlin. He came and had a personal interview with me. His point of view was both dispassionate and resigned. He had no doubts of what the future held for him.

' 'They will get me, Sir Henry,' he said. 'Not a doubt of it.' He was a big man with a fine head and a very deep voice, with only a slight guttural intonation to tell of his nationality. 'That is a foregone conclusion. It does not matter, I am prepared. I faced the risk when I undertook this business. I have done what I set out to do. The organisation can never be gotten together again. But there are many members of it at liberty, and they will take the only revenge they can - my life. It is simply a question of time, but I am anxious that that time should be as long as possible. You see, I am collecting and editing some very interesting material - the result of my life's work. I should like, if possible, to be able to complete my task.'

'He spoke very simply, with a certain grandeur which 1 could not but admire. I told him we would take all precautions, but he waved my words aside.

' 'Some day, sooner or later, they will get me,' he repeated. 'When that day comes, do not distress yourself. You will, I have no doubt, have done all that is possible.' '

'He then proceeded to outline his plans which were simple enough. He proposed to take a small cottage in the country where he could live quietly and go on with his work. In the end he selected a village in Somerset - King's Gnaton, which was seven miles from a railway station and singularly untouched by civilisation. He bought a very charming cottage, had various improvements and alterations made, and settled down there most contentedly. His household consisted of his niece, Greta; a secretary; an old German servant who had served him faithfully for nearly forty years; and an outside handy man and gardener who was a native of King's Gnaton.'

'The four suspects,' said Dr. Lloyd softly.

'Exactly. The four suspects. There is not much more to tell. Life went on peacefully at King's Gnaton for five months and then the blow fell. Dr. Rosen fell down the stairs one morning and was found dead about half an hour later. At the time the accident must have taken place, Gertrud was in her kitchen with the door closed and heard nothing - so she says. Fraulein Greta was in the garden, planting some bulbs - again, so she says. The gardener, Dobbs, was in the small potting shed having his elevenses - so he says; and the secretary was out for a walk, and once more there is only his own word for it. No one had an alibi - no one can corroborate anyone else' s story. But one thing is certain. No one from outside could have done it, for a stranger in the little village of King's Gnaton would be noticed without fail. Both the back and the front doors were locked, each member of the household having his own key. So you see it narrows down to those four. And yet each one seems to be above suspicion. Greta, his own brother's child. Gertrud, with forty years of faithful service. Dobbs, who has never been out of King's Gnaton. And Charles Templeton, the secretary -'

'Yes,' said Colonel Bantry, 'what about him? He seems the suspicious person to my mind. What do you know about him? '

'It is what I knew about him that put him completely out of court - at any rate, at the time,' said Sir Henry gravely. 'You see, Charles Templeton was one of my own men.'

'Oh!' said Colonel Bantry, considerably taken aback.

'Yes. I wanted to have someone on the spot, and at the same time I didn't want to cause talk in the village. Rosen really needed a secretary. I put Templeton on the job. He's a gentleman, he speaks German fluently, and he's altogether a very able fellow.'

'But, then, which do you suspect?' asked Mrs. Bantry in a bewildered tone. 'They all seem so - well, impossible.'

'Yes, so it appears. But you can look at the thing from another angle. Fraulein Greta was his niece and a very lovely girl, but the war has shown us time and again that brother can turn against sister, or father against son, and so on, and the loveliest and gentlest of young girls did some of the most amazing things. The same thing applies to Gertrud, and who knows what other forces might be at work in her case? A quarrel, perhaps, with her master, a growing resentment all the more lasting because of the long faithful years behind her. Elderly women of that class can be amazingly bitter sometimes. And Dobbs? Was he right outside it because he had no connection with the family? Money will do much. In some way Dobbs might have been approached and bought.

'For one thing seems certain: Some message or some order must have come from outside. Otherwise, why five months immunity? No, the agents of the society must have been at work. Not yet sure of Rosen's perfidy, they delayed till the betrayal had been traced to him beyond any possible doubt. And then, all doubts set aside, they must have sent their message to the spy within the gates - the message that said, 'Kill.' '