"How old were your children?" asked Mrs Sarah Fox. "How many had you?" The three people sitting with her in the dimly-lit farmhouse held their breath and waited.
A few moments later, according to the witnesses, four distinct knocks were heard apparently coming from the left-hand wall. A pause and then six more.
"That means two children, one four and one six," said Mrs Fox, making a careful note. Today, those notes, made by an American housewife nearly a century ago, are part of one of the most celebrated cases on record of apparent contact with the dead.
What has become known as the case of the murdered ghost still attracts psychical investigators to the rambling farmhouse at Hydesville, near the US city of Boston, seeking evidence to confirm or discredit Mrs Fox's claims that a murder victim returned from beyond the grave. Nowadays they are disappointed but it wasn't always so.
Until her death in 1930 Mrs Fox continued to declare that she had no doubt that she had communicated with the dead. "I am not a woman given to flights of imagination," she wrote in a preface to her book of notes.
"I have only recorded what I and other witnesses heard. It is up to readers to draw their own conclusions but for me the proof is well nigh conclusive."
It was in the spring of 1916 that John Fox, a farmer, his wife Sarah and their two children moved into the Hydesville farm and after only two weeks the noises apparently began. According to the family, they varied from tapping sounds to heavy rumbling and the children became so disturbed that their beds were moved into their parents' room.
John Fox, whose entire savings had gone into the farm, was determined not to be frightened away. He was certain there was a rational explanation and was determined to find it, even if it meant taking the building apart piece by piece.
But the most exhaustive search yielded no obvious solution and as time went by the mysterious noises grew even louder and more frequent until it was almost impossible to get an unbroken night's sleep.
Then one night the Foxs' younger daughter Rebecca clapped her hands and challenged the ghost -or whatever it was- to imitate her. She claimed that her clap was immediately repeated, the noise apparently coming from mid-air.
Mrs Fox was to write: "It was then that I began to realise that the spirit was benevolent and perhaps in need of help. I began to ask it questions which involved numbers of taps and in nearly every case I got a reply.
"I asked it to give two taps if it was a spirit, and it replied immediately with two sharp knocks. Growing more confident, I put further questions, indicating the number of taps I needed for an answer.
"Over the weeks I learned that the spirit was of a man who had been murdered at the age of 31 in 1822. He was then buried somewhere in the house."
Further questions revealed that the victim was a tradesman who had visited the house and had been murdered after a quarrel.
After this, John Fox and several neighbours descended into the cellar and dug up the floor to a depth of several feet but no remains were found.
Neighbours who began to claim that the Fox family had made up the story were invited to hear the noises for themselves, and left convinced and astounded.
It was a matter of great regret to Mrs Fox that she never found proof of the spirit's allegations and after her death, the farm remained vacant for four years.
It became a playground for local children and in June 1934 a group of youngsters were playing in the cellar when without warning one of the walls crumbled and fell, pinning a child under a pile of rubble.
Help arrived and the youngster was not seriously hurt and was quickly freed. As rescuers flashed their torches around the cellar it was noticed that the fallen wall had been a false one.
Now a cavity was revealed behind it and inside was the skeleton of a man later identified as being at least 100 years old. No one ever found who he was, and a few years later the house was modified and made into a small hotel. The skeleton was buried in consecrated ground and from then on no one was again disturbed by the noise and knocking of what Mrs Fox was convinced were the cries for help of a restless ghost. The murder victim, it seemed, had found peace at last.