It is Upstairs Downstairs crossed with Cluedo. In the laconic note dated Sunday 4 August, 1901, Thomas Benjamin Swift claims he killed his maid because she was threatening to reveal their affair. He says he plans to commit suicide because of the guilt.
The note was found under the floorboards on the first floor of the former grocer's in Wrawby Road, Brigg, by workmen renovating it.
The discovery of Molly Brown's tragic fate, which occurred in the same year as Queen Victoria's death, 'amazed' the local developer who had bought the property about five years ago, according to William Downing, of the agency Dickinson, Davy and Markham, which is trying to let the property.
Mr Downing said he did not know whether the shop's owner, who does not want to be named, had checked the deeds to establish whether the house was once owned by the author, or carried out tests to carbon-date the letter.
''What I do know is that 4 August in 1901 did fall on a Sunday,' he said. 'It could be that Swift got away with the perfect murder.'
Local historians were keeping a discreetly doubtful stance on the question yesterday. At Scunthorpe library, an employee confirmed that a man had checked the local newspapers and parish register without finding any evidence to back up the claims.
The most likely public source to help confirm the story - census returns for 1901, which record the occupants of an address - are not due to be released until 2001 for reasons of privacy.
'I wouldn't like to say whether it could be true or not,' the librarian added. 'We've had a lot of hoaxes - the Hitler diaries, and the Jack the Ripper documents. Let's just say I'm keeping an open mind.'
Lincolnshire police, who are trying to find a former policeman old enough to have heard stories of the period, could not shed any light on the mystery.
'Force policy now is that every murder, whether solved or unsolved, remains on file. But that policy only dates back a few years and we only keep limited records of crimes dating back to the start of the century in our force museum,' said a spokesman.
'There is nothing on file under the name Thomas Benjamin Swift, but that doesn't mean the murder did not take place. It is almost certain that we would not have kept records of a missing maid for 90 years.'
Until the mystery is solved, the note will stay in its place of honour, on the wall of the room where it was found.
Another question is also outstanding - whether the Rev Geoffrey Neale, of St John's Church in Brigg, has carried out Mr Swift's last request.
What Thomas Swift wrote
'To whom it may cocern (sic): I, Thomas Benjamin Swift, now and on this day of Sunday in the year of our Lord 1901, do hereby confess to the murder of Molly Brown, maid of the establishment.
'We had meetings, and she thrtend (sic) to reveal that she had conceived. This I could not allow. Now I cannot live with the burden of my guillt (sic) any longer, so I have decieded (sic) to end it all. Whosoever should find this letter, and make all haste to the parish vicar so that he can pray for my forgiveness. I leave this establishment and all within.'Reuse content