Mary Frances Avery was born on July 29, 1899, in Rahway, New Jersey. She faced a difficult childhood. Both of her parents passed away when she was young. After their deaths, she and her siblings were raised by their maternal grandparents. As a child, she was not known for being a good student, and she had few friends, often choosing to keep to herself.

Mary had a complicated relationship with her siblings. She became estranged from her two sisters after a disagreement about their parents' inheritance. This conflict likely added to her feelings of isolation. At the age of 15, she moved to Newark, New Jersey, where she completed her high school education.

In 1917, Mary met John Creighton, who was a sailor and had served in the First World War. They married on December 25, 1918. Following their marriage, they lived with John's parents in Newark. The couple had a daughter named Ruth in 1918. Over the next few years, various family members faced health issues, which caused tension in their home. In 1920, John's mother became ill and later died. This situation likely added stress to Mary’s life, as she dealt with the responsibilities of family and the dynamics in the household.

After a series of family tragedies, including the deaths of her mother-in-law, father-in-law, and her brother Raymond, suspicions arose around Mary. She inherited money from some of these deceased family members, which fueled rumors and investigations. Despite the attention and speculation, she was acquitted in trials related to these deaths.

Feeling unable to stay in Newark due to the surrounding suspicion, Mary and John moved to Baldwin, Long Island. They expanded their household by inviting the Appelgate family to live with them. This decision brought new relationships into their lives, as their daughter Ruth became friends with the Appelgates' daughter, Agnes. 

Mary Frances Creighton lived in a crowded household with her husband, John, and his parents in Newark. In 1920, her mother-in-law fell ill and died after being admitted to the hospital. This was followed by the death of her father-in-law in 1921 and her brother Raymond in 1923. Authorities began to suspect foul play after noticing that Creighton was the beneficiary of her brother's life insurance policy.

In 1923, Creighton and John were tried for the death of Raymond but were acquitted due to a lack of evidence. The same year, she was also tried for the murder of her mother-in-law. Again, there was insufficient evidence to convict her, and she was released. Creighton’s relationship with her husband’s parents continued to be tense.

The family moved to Baldwin, Long Island, seeking a fresh start. There, they befriended their neighbors, Everett and Ada Appelgate. In September 1935, Ada became ill and died after a brief hospitalization. The circumstances surrounding her death raised suspicions. An anonymous tip led authorities to examine her case closely.

An autopsy on Ada revealed traces of arsenic, which prompted the arrest of Creighton. During the investigation, it became known that Creighton had been involved in sexual misconduct with her daughter, Ruth, and had allegedly poisoned Ada so Ruth could marry Everett legally.

In early 1936, both Creighton and Everett were convicted of first-degree murder. They were sentenced to death by electrocution. On July 16, 1936, Creighton was executed at Sing Sing Prison. Reports indicated that she was unconscious at the time of the execution.