Sarah Malcolm was born in late May 1710 in County Durham, Great Britain, to an Anglo-Irish family. Following the death of her mother, she moved to Dublin with her father, who was a businessman. Despite receiving a proper education, Sarah sought employment in London as a domestic servant. She worked in various households, including as a laundress for residents above the Inns of Court near Temple Bar. It was during this period that she became acquainted with Lydia Duncomb, an 80-year-old widow residing in the Inner Temple.

Sarah Malcolm was born in late May 1710 in County Durham, Great Britain, to an Anglo-Irish family. Following the death of her mother, she moved to Dublin with her father, who was a businessman. Despite receiving a proper education, Sarah sought employment in London as a domestic servant. She worked in various households, including as a laundress for residents above the Inns of Court near Temple Bar. It was during this period that she became acquainted with Lydia Duncomb, an 80-year-old widow residing in the Inner Temple.

On the night of February 4, 1733, a gruesome triple murder occurred in the residence of Lydia Duncomb within London's Inner Temple. Lydia Duncomb was found strangled, her companion Elizabeth Harrison, approximately 60 years old, was also strangled, and their maid, Ann Price, around 17 years old, had her throat slit. The following day, the murders were discovered, and suspicion quickly fell upon Sarah Malcolm due to her prior employment and proximity to the victims.

Upon searching Sarah's room, authorities discovered items belonging to the deceased women, including a silver tankard and blood-stained clothing. Further investigation revealed that she had attempted to bribe a prison turnkey with coins hidden in her hair. Sarah was arrested on February 5, 1733, and taken to Newgate Prison.

During her trial at the Old Bailey on February 23, 1733, Sarah defended herself, admitting to participating in the robbery but denying involvement in the murders. She claimed that the blood on her clothing was menstrual, not from the victims. Despite her assertions, the jury found her guilty of murder after deliberating for only 15 minutes. She was sentenced to death by hanging.

While awaiting execution, Sarah was visited by the artist William Hogarth, who sketched her portrait in Newgate Prison. This portrait contributed to her notoriety and has been referenced in various historical accounts.

Sarah Malcolm was executed on March 7, 1733, near the scene of the crime in Fleet Street, London. Her case has been cited in discussions of women's roles in crime during the 18th century and has been the subject of various historical analyses.