Agnes Naismith holds a prominent place in the story, given that she was accused alongside Katherine Campbell at the beginning of Christian Shaw's malady. Various local sources tell us that she probably resided in Kilpatrick, on the other side of the river from Bargarran house. According to the story, Naismith was the key individual who was responsible for the child's descent into illness, and it would seem she had a relationship of sorts with the maid Katherine Campbell. Agnes Naismith was an elderly woman, impoverished, with a reputation in the local area for being someone who you did not cross lightly.

Naismith would have been a regular visitor to Bargarran House, as well as other steadings in the local region, in search of food and materials to help her in her daily life. It is likely that she existed on the margins. On the 21st of August 1696, just four days after Katherine Campbell had cursed the young girl, Naismith arrived at Bargarran house, very early in the morning. The story goes that she found Christian Shaw in the courtyard with her younger sister. Naismith then asked after Christian Shaw's health, and what her age was. Both pieces of information were given freely. Her visit would not have been an unusual event for Christian Shaw, who would have been accustomed to people approaching the house for food at a time when pressures on the land meant that more people were seeking charity. Apparently, Naismith did not wait for alms on this occasion.

The next evening, Christian Shaw experienced her first fit. She was said to have flown over her bed and into a bystander in her bedchamber. She suffered excruciating pains, became paralysed, before convulsing violently. These symptoms continued for eight days. Soon, the child was blaming Naismith for cutting her side and tormenting her. Naismith's recent visit to the house would have been remembered, as would her questions to the child.  Naismith was summoned to Bargarran House twice to answer to the charges. Without being asked to do so, Naismith prayed for the young girl's health to improve. Once she had done this, Christian Shaw declared that Naismith no longer tormented her. Indeed, the girl claimed that Naismith began to buffet her from the worst of the assaults from her other invisible tormentors.

Despite this, Naismith was found guilty due to the weight of witness evidence against her at the trial. She was deemed responsible not only for the bewitching of Christian Shaw, but of being one of the more important members of the local crew of witches that were said to be terrorising the area. She never confessed to this charge, even to the end. Just before she was hanged, it is said that she laid a curse on all those who stood witness to her execution. Naismith's curse can be directly linked to the horseshoe that was laid some years later. Even in death, her legacy continues.