his flattened flaxen head, but stood looking down at the dead men with a shade of something like indifference on his large froglike face. Only when he looked at the cigar-ash, which the priest had preserved, he touched it with one finger; then he seemed to stand even stiller than before; but in the shadow of his face his eyes for an instant seemed to shoot out telescopically like one of his own microscopes. He had certainly realized or recognized something; but he said nothing.
'I don't know where anyone is to begin in this business,' said the Master.
'I should begin,' said Father Brown, 'by asking where these unfortunate men had been most of the time today.'
'They were messing about in my laboratory for a good time,' said Wadham, speaking for the first time. 'Baker often comes up to have a chat, and this time he brought his two patrons to inspect my department. But I think they went everywhere; real tourists. I know they went to the chapel and even into the tunnel under the crypt, where you have to light candles; instead of digesting their food like sane men. Baker seems to have taken them everywhere.'
'Were they interested in anything particular in your department?' asked the priest. 'What were you doing there just then?'
The Professor of Chemistry murmured a chemical formula beginning with 'sulphate', and ending with something that sounded like 'silenium'; unintelligible to both his hearers. He then wandered wearily away and sat on a remote bench in the sun, closing his eyes, but turning up his large face with heavy forbearance.
At his point, by a sharp contrast, the lawns were crossed by a brisk figure travelling as rapidly and as straight as a bullet; and Father Brown recognized the neat black clothes and shrewd doglike face of a police-surgeon whom he had met in the poorer parts of town. He was the first to arrive of the official contingent.
'Look here,' said the Master to the priest, before the doctor was within earshot. 'I must know something. Did you mean what you said about Communism being a real danger and leading to crime?'
'Yes,' said Father Brown smiling rather grimly, 'I have really noticed the spread of some Communist ways and influences; and, in one sense, this is a Communist crime.'
'Thank you,' said the Master. 'Then I must go off and see to something at once. Tell the authorities I'll be back in ten minutes.'
The Master had vanished into one of the Tudor archways at just about the moment when the police-doctor had reached the table and cheerfully recognized Father Brown. On the latter's suggestion that they should sit down at the tragic table, Dr Blake threw one sharp and doubtful glance at the big, bland and seemingly somnolent chemist, who occupied a more remote seat. He was duly informed of the Professor's identity, and what had so far been gathered of the Professor's evidence; and listened to it silently while conducting a preliminary examination of the dead bodies. Naturally, he seemed more concentrated on the actual corpses than on the hearsay evidence, until one detail suddenly distracted him entirely from the science of anatomy.
'What did the Professor say he was working at?' he inquired.
Father Brown patiently repeated the chemical formula he did not understand.
'What?' snapped Dr Blake, like a pistol-shot. 'Gosh! This is pretty frightful!'
'Because it's poison?' inquired Father Brown.
'Because it's piffle,' replied Dr. Blake. 'It's simply nonsense. The Professor is quite a famous chemist. Why is a famous chemist deliberately talking nonsense?'
'Well, I think I know that one,' answered Father Brown mildly. 'He is talking nonsense, because he is telling lies. He is concealing something; and he wanted specially to conceal it from these two men and their representatives.'
The doctor lifted his eyes from the two men and looked across at the almost unnaturally immobile figure of the great chemist. He might almost have been asleep; a garden butterfly had settled upon him and seemed to turn his stillness into that of a stone idol. The large folds of his froglike face reminded the doctor of the hanging skins of a rhinoceros.
'Yes,' said Father Brown, in a very low voice. 'He is a wicked man.'
'God damn it all!' cried the doctor, suddenly moved to his very depths. 'Do you mean that a great scientific man like that deals in murder?'
'Fastidious critics would have complained of his dealing in murder,' said the priest dispassionately. 'I don't say I'm very fond of people dealing in murder in that way myself. But what's much more to the point — I'm sure that these poor fellows were among his fastidious critics.'
'You mean they found his secret and he silenced them?' said Blake frowning. 'But what in hell was his secret? How could a man murder on a large scale in a place like this?'
'I have told you his secret,' said the priest. 'It is a secret of the soul. He is a bad man. For heaven's sake don't fancy I say that because he and I are of opposite schools or traditions. I have a crowd of scientific friends; and most of them are heroically disinterested. Even of the most sceptical, I would only say they are rather irrationally disinterested. But now and then you do get a man who is a materialist, in the sense of a beast. I repeat he's a bad man. Much worse than — ' And Father Brown seemed to hesitate for a word.
'You mean much worse than the Communist?' suggested the other.
'No; I mean much worse than the murderer,' said Father Brown.
He got to his feet in an abstracted manner; and hardly realized that his companion was staring at him.
'But didn't you mean,' asked Blake at last, 'that this Wadham is the murderer?'
'Oh, no,' said Father Brown more cheerfully. 'The murderer is a much more sympathetic and understandable person. He at least was desperate; and had the excuses of sudden rage and despair.'
'Why,' cried the doctor, 'do you mean it was the Communist after all?'
It was at this very moment, appropriately enough, that the police officials appeared with an announcement that seemed to conclude the case in a most decisive and satisfactory manner. They had been somewhat delayed in reaching the scene of the crime, by the simple fact that they had already captured the criminal. Indeed, they had captured him almost at the gates of their own official residence. They had already had reason to suspect the activities of Craken the Communist during various disorders in the town; when they heard of the outrage they felt it safe to arrest him; and found the arrest thoroughly justified. For, as Inspector Cook radiantly explained to dons and doctors on the lawn of Mandeville garden, no sooner was the notorious Communist searched, than it was found that he was actually carrying a box of poisoned matches.
The moment Father Brown heard the word 'matches', he jumped from his seat as if a match had been lighted under him.
'Ah,' he cried, with a sort of universal radiance, 'and now it's all clear.'
'What do you mean by all clear?' demanded the Master of Mandeville, who had returned in all the pomp of his own officialism to match the pomp of the police officials now occupying the College like a victorious army. 'Do you mean you are convinced now that the case against Craken is clear?'
'I mean that Craken is cleared,' said Father Brown firmly, 'and the case against Craken is cleared away. Do you really believe Craken is the kind of man who would go about poisoning people with matches?'
'That's all very well,' replied the Master, with the troubled expression he had never lost since the first sensation occurred. 'But it was you yourself who said that fanatics with false principles may do wicked things. For that matter, it was you yourself who said that Communism is creeping up everywhere and Communistic habits spreading.'
Father Brown laughed in a rather shamefaced manner.
'As to the last point,' he said, 'I suppose I owe you all an apology. I seem to be always making a mess of things with my silly little jokes.'
'Jokes!' repeated the Master, staring rather indignantly.
'Well,' explained the priest, rubbing his head. 'When I talked about a Communist habit spreading, I only meant a habit I happen to have noticed about two or three times even today. It is a Communist habit by no means confined to Communists. It is the extraordinary habit of so many men, especially Englishmen, of putting other people's matchboxes in their pockets without remembering to return them. Of course, it seems an awfully silly little trifle to talk about. But it does happen to be the way the crime was committed.'
'It sounds to me quite crazy,' said the doctor.
'Well, if almost any man may forget to return matches, you can bet your boots that Craken would forget to return them. So the poisoner who had prepared the matches got rid of them on to Craken, by the simple process of
