In 1843, a Canadian housemaid named Grace Marks was convicted, along with James McDermott, for murdering their employer, Thomas Kinnear, and his pregnant lover, Nancy Montgomery.
At the time of the murder, Grace was only sixteen years old. Thomas Kinnear, the murdered gentleman farmer, was fond of his housekeeper, Nancy Montgomery; in fact, both were lovers at the time of their death. James McDermott, the man alleged to have carried out the murders himself, was a stable hand on the Kinnear property. He was rumored to have held romantic feelings towards Grace, but it was never substantiated by Grace herself as to whether the sentiments were fully returned.
It was clear that there was no love lost between both Nancy and Grace. While Nancy was suspicious of Kinnear's predilection for the teenage maid, Grace was resentful of the housekeeper's life of relative ease and luxury despite her position in the household. As McDermott's own jealousy got the better of him, the hapless stable hand supposedly agreed to do away with Nancy in exchange for Grace's romantic fidelity to him.
Accordingly, McDermott struck Nancy in the head with an axe before throwing her down the cellar stairs. As Nancy pleaded for her life, it was rumored that both McDermott and Grace strangled Nancy to death. When Kinnear returned from his trip, McDermott shot him in the heart despite Grace's pleading for Kinnear's life. Both Nancy and McDermott then fled to Toronto with Kinnear's horse and wagon. They also took with them their former employer's gold and silver.
At the hearing, both Grace and McDermott blamed the other for instigating the murders. However, McDermott was hanged and his body later donated to science for dissection; Grace was sentenced to life imprisonment for her role in the murders.