The appearance of the letter is unexpected as the house has been deserted for a while and Mrs Drover knows of no-one who could have left the letter there, not even the caretaker, as he is meant to be on holiday.
The appearance of the letter is all the more odd as it is lying on an otherwise dusty table, as if someone has deliberately left it there; it hasn't just fallen through the letterbox. Mrs Drover is baffled, but she tries not to give in to fearful speculation: 'On the supernatural side of the letter's entrance she was not permitting her mind to dwell'.
However, she becomes increasingly disquieted after reading the letter, as it purports to be from her long-lost lover whom she remembers as a rather sinister character. He writes of a a pledge to meet again to remember their anniversary, on that very day. This is all part of the ominous build-up to the climax of the story when Mrs Drover is driven off by a strange menacing figure in a car which she first innocently assumes to be her taxi.
It is never quite revealed whether the man who comes to claim Mrs Drover is alive or returned from the dead, and the story ends on this grimly intriguing note. However, the earlier inexplicable appearance of the letter, coupled with the fact that her lover was presumed dead in the First World War, inclines the story towards the supernatural.