Ottilie "Tillie" Klimek, born Otylia Gburek in 1876 in Poland, immigrated to the United States with her parents as an infant, settling in Chicago's "Little Poland" neighborhood. In 1895, she married her first husband, Jozef Mitkiewicz.

Tillie's criminal activities began with the death of her first husband, Jozef Mitkiewicz, in 1914, who died after a sudden illness; his death was attributed to heart trouble at the time. She remarried quickly, taking Joseph Ruskowski as her second husband, who also died shortly thereafter under similar circumstances. Tillie was known to claim she had precognitive dreams predicting the deaths of her victims, which in reality were orchestrated poisonings using arsenic.

Her third husband, Frank Kupczyk, whom she married in 1921, also fell ill and died. Before his death, Tillie had ominously told neighbors that he "would not live long," and even purchased a coffin in anticipation. She married her final husband, Joseph Klimek, later in 1921. When he became ill, doctors suspected arsenic poisoning, leading to an investigation. Subsequent exhumations of her previous husbands revealed lethal doses of arsenic, confirming suspicions of foul play.

Tillie was arrested on October 27, 1922, and in March 1923, she was convicted of the murder of Frank Kupczyk and sentenced to life imprisonment—the harshest sentence imposed on a woman in Cook County at that time. She was incarcerated at Joliet Correctional Center, where she died on November 20, 1936.