The Killer and the Slain

I, John Ozias Talbot, aged thirty-six years and three months, being in my perfectly sane mind, wish to write down this statement.
I do so entirely and solely for my own benefit and profit--in fact, for the quietening of my disturbed mind. It is most improbable that anyone other than myself will read this document, but should anything happen to me and I die without destroying this writing, I wish the reader, whoever he or she may be, to realize fully that no one could conceivably be of a more complete mental sanity and honest matter-of-fact common sense than I am at this moment.
It is because I wish to show this self-evident fact to myself and, if need be, to the whole world (after my death) that I write this down. There will be many minute and apparently insignificant facts and details in this record because circumstantial facts are in this matter the thing! I have suffered during these preceding months certain experiences so unbelievable that were I not sane, and were many of the facts not so commonplace, my sanity might be doubted. It is not to be doubted. I am as sane as any man in the United Kingdom.