`Has anything escaped me?' I asked with some self-importance. `I trust that there is nothing of consequence which I have overlooked?'

`I am afraid, my dear Watson, that most of your conclusions were erroneous.

When I said that you stimulated me I meant, to be frank, that in noting your fallacies I was occasionally guided towards the truth. Not that you are entirely wrong in this instance. The man is certainly a country practitioner. And he walks a good deal.'

`Then I was right.'

`To that extent.'

`But that was all.'

`No, no, my dear Watson, not all - by no means all. I would suggest, for example, that a presentation to a doctor is more likely to come from a hospital than from a hunt, and that when the initials ``C.C.'' are placed before that hospital the words ``Charing Cross'' very naturally suggest themselves.'

`You may be right.'

`The probability lies in that direction. And if we take this as a working hypothesis we have a fresh basis from which to start our construction of this unknown visitor.'

`Well, then, supposing that ``C.C.H.'' does stand for ``Charing Cross Hospital,'' what further inferences may we draw?'

`Do none suggest themselves? You know my methods. Apply them!'

`I can only think of the obvious conclusion that the man has practised in town before going to the country.'

`I think that we might venture a little farther than this. Look at it in this light. On what occasion would it be most probable that such a presentation would be made? When would his friends unite to give him a pledge of their good will? Obviously at the moment when Dr. Mortimer withdrew from the service of the hospital in order to start in practice for himself. We know there has been a presentation. We believe there has been a change from a town hospital to a country practice. Is it, then, stretching our inference too far to say that the presentation was on the occasion of the change?'

`It certainly seems probable.'

`Now, you will observe that he could not have been on the staff of the hospital, since only a man well- established in a London practice could hold such a position, and such a one would not drift into the country. What was he, then? If he was in the hospital and yet not on the staff he could only have been a house-surgeon or a house-physician - little more than a senior student. And he left five years ago - the date is on the stick. So your grave, middle-aged family practitioner vanishes into thin air, my dear Watson, and there emerges a young fellow under thirty, amiable, unambitious, absent-minded, and the possessor of a favourite dog, which I should describe roughly as being larger than a terrier and smaller than a mastiff.'

I laughed incredulously as Sherlock Holmes leaned back in his settee and blew little wavering rings of smoke up to the ceiling.

`As to the latter part, I have no means of checking you,' said I, `but at least it is not difficult to find out a few particulars about the man's age and professional career.' From my small medical shelf I took down