‘I told the police so, and invited them to make tests. Actually there are two typewriters here. My secretary, Miss Bathwell, has one and I have one of my own. The police, although they seemed not very eager to remain in College for long – they found a plethora of students embarrassing – tested both machines and assured themselves that neither had been used for the anonymous letters. And that reminds me. On the same occasion as he did the typing, Mr Emming borrowed a book from the College library which I believe he has not yet returned.’

‘What book?’ Mrs Bradley enquired.

‘Nature’s Traffic Lights.’

‘I beg your pardon?’

‘I know, but the book is called that. It describes and illustrates various poisonous berries and fungi. It is really a book for young children, but the students, especially those from urban areas, find it very useful in identifying such plants as the deadly nightshade, for example.

‘Belladonna!’ exclaimed Miss Bagthorpe dramatically. ‘Wasn’t that the poison …?’

‘Which killed Mrs Dalby Whittier? Yes, it was. And you lent the book to Emming, and it was found at the Fullaloves’ bungalow. I don’t know that we can use it in evidence, but it certainly offers some interesting corroborative detail. It certainly does not seem a book which one grown man would ordinarily lend another. A great light dawns on me, by the way. Emming is a Londoner. Tiny Fullalove has spent much of his life in India. Ed Brown is known to be knowledgeable about wild birds and may equally be so about wild plants. What if Ed’s guilty recollection is of being asked to identify the berries of the deadly nightshade? The question could have been asked casually and among such a host of others … and the name of the poison itself, belladonna, is probably entirely unknown to Ed, so I may be wrong. On the other hand, it is amazing what country people do know.’

‘I believe you have got something there,’ said Sally to her aunt on the homeward drive. ‘You had better jog Ed Brown’s memory.’

‘It will have to be done circumspectly, then,’ Mrs Bradley replied. ‘I cannot, at this stage, put a leading question. I must give the matter some thought.’

Sally went off next day, and Mrs Bradley, having pushed a note under Will North’s door, went by car to Pinxworth and then walked. George put the car up at the public house, and, unknown to his employer until she stopped to admire the view (and, turning, saw him), trudged stolidly behind her with one of Will North’s sporting guns sloped professionally over his forearm. Unknown to his employer, he had kept this gun in the car since the visit to Oxford.