‘As far as I can tell, the house was not entered forcibly from the outside. That seems to point to some member of my household, and yet I cannot believe—’ He broke off abruptly, then began again, his voice very grave.

‘Mr Blunt, I must place myself in your hands unreservedly. I dare not go to the police in the matter. Of my three servants I am almost entirely sure. They have served me long and faithfully. Still, one never knows. Then I have living with me my two nephews, Bertram and Henry. Henry is a good boy—a very good boy—he has never caused me any anxiety, an excellent hard-working young fellow. Bertram, I regret to say, is of quite a different character—wild, extravagant, and persistently idle.’

‘I see,’ said Tommy thoughtfully. ‘You suspect your nephew Bertram of being mixed up in this business. Now I don’t agree with you. I suspect the good boy—Henry.’

‘But why?’

‘Tradition. Precedent.’ Tommy waved his hand airily. ‘In my experience, the suspicious characters are always innocent—and vice versa, my dear sir. Yes, decidedly, I suspect Henry.’

‘Excuse me, Mr Blunt,’ said Tuppence, interrupting in a deferential tone. ‘Did I understand Dr Bower to say that these notes on—er—obscure alkaloids—are kept in the desk with the other papers?’

‘They are kept in the desk, my dear young lady, but in a secret drawer, the position of which is known only to myself. Hence they have so far defied the search.’

‘And what exactly do you want me to do, Dr Bower?’ asked Tommy. ‘Do you anticipate that a further search will be made?’

‘I do, Mr Blunt. I have every reason to believe so. This afternoon I received a telegram from a patient of mine whom I ordered to Bournemouth a few weeks ago. The telegram states that my patient is in a critical condition, and begs me to come down at once. Rendered suspicious by the events I have told you of, I myself despatched a telegram, prepaid, to the patient in question, and elicited the fact that he was in good health and had sent no summons to me of any kind. It occurred to me that if I pretended to have been taken in, and duly departed to Bournemouth, we should have a very good chance of finding the miscreants at work. They—or he—will doubtless wait until the household has retired to bed before commencing operations. I suggest that you should meet me outside my house at eleven o’clock this evening, and we will investigate the matter together.’

‘Hoping, in fact, to catch them in the act.’ Tommy drummed thoughtfully on the table with a paper-knife. ‘Your plan seems to me an excellent one, Dr Bower. I cannot see any hitch in it. Let me see, your address is—?’

‘The Larches, Hangman’s Lane—rather a lonely part, I am afraid. But we command magnificent views over the Heath.’