Mary Ann Cotton, an English woman who lived during the Mid 1800’s in County Durham, had a habit of marrying men and then collecting the insurance policy when they died.

Which they invariably did.

At 20, Mary Ann married her first husband, collier laborer, William Mowbry. Of the five children she bore him, four of them died and none of their deaths were registered as per British law. She bore four more but they passed of gastrointestinal issues. William also died from the same malady. Mary Ann collected insurance on all of them.

After William passed, Mary Ann and her surviving child, Isabella, moved to another part of the country where she met and married a sickly gentleman, George Ward. She sent Isabella to live with her mother and soon after, George died of cholera. Though George was never very well, the doctor on the case was surprised by his sudden passing. Perhaps Mary Ann was also surprised… or perhaps not as she also collected the insurance benefit for poor, invalid, George.

Her third husband, James Robinson turned to Mary Ann, (his housekeeper), after his wife died and she became pregnant. During this time, Mary Ann’s mother came down with hepatitis and Mary Ann went to nurse her back to health, though, perhaps that’s a stretch, as soon as her mother recovered from hepatitis, she came down with a mysterious stomach ailment that killed her. Back to James Mary Ann went, along with Isabella and the two were married. Unfortunately, James’ children all died at the same time as her daughter, Isabella. Luckily, Isabella was insured and Mary Ann was able to collect on her. They had a son, George. Soon James became suspicious when Mary Ann began to insist that he take out life insurance. When he discovered that she had run up debt behind his back and was having their son pawn the family valuables, he threw her out and retained custody of George, probably saving both their lives.

Desperate and homeless, Mary Ann turned to her friend, Margaret who introduced her to her brother, Frederick Cotton, who had recently lost his wife. Margaret was raising her nieces and nephews for her brother, but she soon passed from an indeterminate stomach issue and Mary Ann was there to comfort the bereaved Frederick, who as you may have guessed, soon passed away from gastric issues, leaving Mary Ann with the insurance money.

But wait, there’s more.

Mary Ann took on two lovers and one of them died after changing his will, leaving Mary Ann with everything. One of the Cotton boys was still with her and she tried to get a parish official to put him in a workhouse. He died five days after the attempt failed and the official went to the police to have them investigate. The local newspaper latched on to the story and soon discovered that Mary Ann had lost four husbands, 11 children, her mother and a lover. Mary Ann was soon arrested, but the trial was delayed because Mary Ann was pregnant. The lucky child was taken away soon after birth, Mary Ann was found guilty of one murder, though suspected of many more.
She was put to death on March 24th 1873.
Britians first female serial killer was immortalized in this film, Dark Angel. You can read more about her here.

https://en.wikipedia.org/wiki/Dark_Angel_(British_TV_series)

https://www.britannica.com/biography/Mary-Ann-Cotton