Margaret Waters was born in 1835 in Brixton, England. She was married and lived in relatively comfortable circumstances until the death of her husband in 1864. Left with £300, she attempted to start a sewing business, which failed, leading to significant financial loss. Subsequently, she began taking in lodgers and eventually turned to baby farming—a practice where individuals accepted infants for a fee, promising care but often leading to neglect or worse.

Waters began advertising in newspapers, offering to adopt unwanted infants for a fee ranging from £5 to £10. Instead of providing care, she administered laudanum, an opiate, to sedate the babies, suppressing their appetites and leading to starvation. This method allowed her to minimize expenses while maximizing profit.

In August 1870, authorities, acting on reports of multiple infant deaths, investigated Waters' residence. They discovered nine infants, five of whom were in critical condition due to malnutrition and opium poisoning. Further investigations linked her to the deaths of several infants, though she was formally charged with the murder of John Walter Cowen.

Waters' trial commenced in September 1870. Despite her claims that the children died of natural causes, the jury found her guilty of willful murder. She was sentenced to death and executed by hanging on October 11, 1870, at Horsemonger Lane Gaol in London. Her sister, Sarah Ellis, was convicted of obtaining money under false pretenses and sentenced to 18 months of hard labor.