THE story of teenage murderess Grace Marks is the ultimate whodunnit mystery.

The 16-year-old Irish maid, along with stable hand James McDermott, 20, was convicted of the brutal murders of their employer Thomas Kinnear and his housekeeper Nancy Montgomery in Canada in 1843.

4 Sarah as Grace in the Netflix series

4 Pictures of Grace and James

Grace and James were found guilty by a jury after just ten minutes deliberation and James was hanged while Grace was locked up for 30 years.

Pretty Grace became one of the most enigmatic and notorious women of 1840s Canada for her supposed role in the sensational double murder.

Her conviction was controversial and sparked much debate about whether Grace was actually involved in the murder, or merely an unwitting accessory.

Her story is the next offering from Netflix and the people behind the Handmaid’s Tale. The six-hour mini-series, Alias Grace, is based on Margaret Atwood’s award-winning novel, and stars Canadian actor Sarah Gadon, True Blood lead Anna Paquin and Thor star Zachary Levi.

Did the young lovers conspire together to butcher their employers? Was Grace an unwilling participant in the slaying, or did she spearhead the whole thing?

The infamous young woman was born and raised in Northern Ireland.

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She was the third eldest of eight children and the family immigrated to Canada in the 1840s when she was just 12.

Her mother died on the voyage and was buried at sea. Her father, John Marks was a stone mason, and said to be an alcoholic and abusive person.

During the murder trial, the story of the teenage killer made headlines all over the world.

4 Anna playing the victim in Alias Grace

In his confession, James said it was Grace who planned the killings and wanted to poison the housekeeper’s porridge after getting fired. He said it was Grace, not him, who strangled Nancy.

He said: “Grace Marks is wrong in stating she had no hand in the murder; she was the means from beginning to end.”

However, Grace said she was coerced into helping James with the murders and that he also tried to shoot her.

4 Kerr as the killer James

There are theories about Grace’s mental state, that she was pretending to be mad to avoid the gallows, or that she was indeed suffering from psychological issues.

Other theories at the time speculated that she was possessed by her dead friend Mary Whitney. There were also arguments that Grace was the one who died, and Mary adopted her name and identity.

Despite the swirling rumours, Grace paid for the crime. She entered the Provincial Penitentiary in Kingston, Ontario on November 19, 1843 and was eventually exonerated after 30 years in jail. She then moved Northern York and no more is known of her.

ALIAS GRACE will be available on Netflix from November 3.