Mary Ann Cotton was born Mary Ann Robson in 1832 in England. She worked as a nursemaid and then as a Sunday-school teacher in her maiden days, which is going to be really terrifying in about four paragraphs.
She married a man named William Mowbray, they popped out nine children in really rapid succession, but five of them died young. Then Mowbray got sick and died, and then two more of her children died. Such things happened. Infant mortality rates were high, lifespans were shorter, and you would periodically get epidemics of typhus, typhoid and cholera that would swoop in and wipe out whole families.
With no one to support her in her widowhood, she took her two surviving children and got a job as a nurse in an infirmary. Not long after she met and married George Ward, but--poor, unlucky Mary Ann--he died within the year, widowing her for the second time. She started dating this guy named Joseph Nattrass, but they broke up, so she moved on. She got a job as a housekeeper to a Mr. James Robinson, who had five children of his own. The week she took up her post, both one of his children and one of hers died. Mary Ann was still an attractive woman only in her early 30s, and she and Robinson had the shared hardship of losing children together, so they married within six months of her hire date.
She sent her last surviving child by her first husband to live with her mother. In 1867 she went to nurse her ailing mother who died shortly thereafter, and Mary Ann came back with her child. That child was suddenly taken ill, as were two of Robinson's surviving four children by his first wife, and all died of gastric fever. By this point, she and Robinson had had two children of their own, one of whom had died.
Guys, this is the point where someone needs to start asking questions. When all of your nine children from your first marriage slowly drop like flies, as does your mother, two husbands, three of your third husband's five children by his first wife, and one of the children you had together . . . that's a lot. That's when you go, "HMMMMMMMMMMMMMMM".
Anyway, in "1869 Robinson discovered that his wife had been trying to borrow money using his name, and his son told him she had been secretly sending him to pawn goods Robinson had given her. He accused her, and she left, taking with her her surviving child and the contents of her Post Office Savings account. She soon abandoned the child, who was later returned to Robinson" (388). This is the only time I will say that abandoning a child was the best thing a mother could possibly do for it.
Still technically married, she hooked up with a guy named Frederick Cotton, who she married bigamously. She took his name, popped out a baby, and moved in with him and his two boys from a previous marriage. Then Joseph Nattrass, the guy she had been seeing before she married Robinson, showed up and decided he's going to be the new couple's lodger. Without doubt, Frederick Cotton had no idea that his new lodger had once been his wife's boy-toy, otherwise he wouldn't have taken him in. But he didn't have to worry about it long, because he died suddenly.
So an old boyfriend moves in and the new husband quickly dies. Nothing suspicious here, let's move on.
She got a job working at a brewery, and then Cotton's eldest son by his first wife, the baby they had together, Nattrass the ex [current?]- boyfriend, and Cotton's sister, Margaret, all died. Guys. How is this not raising any red flags? SERIOUSLY. We've reached parody levels.
So she continued working at the brewery, living with Cotton's remaining son and receiving parish charity money to help with his upkeep, because she's just a poor bereaved widow, after all. Then a parish overseer asked her if she was planning on marrying her boss at the brewery, because apparently this woman is irresistible, and she replied, "It might be so. But the boy is in the way. Perhaps it won't matter, as I won't be troubled long. He'll go like all the rest of the Cotton family." And a week later he died. Okay, did she want to be caught? Or did she think she was invincible, since she had gone so long without attracting notice? I have no idea what would possess her to say something like this.
FINALLY the overseer reported her to the police. I mean, she basically had to reveal her dastardly plan, all wrapped up with a bow and shoved down someone's throat before anyone noticed. She's going to get caught, right? Right!
Oh, no wait.
At first the doctor was all like, "That conversation sounds mighty poison-y. I shall withhold the death certificate until I do an autopsy. Oh, no, my findings show he died of natural causes. I most definitely have stellar medical training." So she gets let off the hook. Sort of. Thankfully, the greedy newspapers had heard of the story and were praying that she was a serial killer so they'd have a good story to print. They refused to let the issue drop. The one time the press's harassment was for the benefit of the nation. They said, "That doctor is a hack. Get someone better to analyze the dead boy." And sure enough, arsenic was found in his body and she was arrested.
A neighbor came forward saying that Mary Ann Cotton had asked her to buy arsenic to, uh, "kill bedbugs". So everyone got to go on a grand ole treasure hunt, digging up the bodies she had left in her wake. They dug up Nattrass. BAM. Arsenic. They dug up the two other Cotton children. BAM. Arsenic. Then they tried to find Cotton's body, but he had been buried in a pauper's grave, so it wasn't marked, and they dug up a dozen coffins and still couldn't find him, and went, "Ugggh, whatever," and decided not to pursue it any further, nor would they bother looking into the Mowbray, Ward and Robinson children deaths because it's too haaaaaaaaaaaaaaard.
By this point Mary Ann Cotton was sitting in jail, seven months pregnant with the child of her boss at the brewery--hey, I guess she IS irresistible after all!--and the trial was postponed until she had given birth
She was very obviously guilty and was sentenced to execution, which was carried out on March 24, 1873. It is entirely possible that some of the people around her could have died from natural causes, but we'll never know the truth because a.) they were too lazy to investigate all of the deaths and b.) science wasn't advanced enough to prove murder in the very advanced stages of decay (arsenic was found in a shocking number of household products back then, so they couldn't prove intent even if they did find traces of it). Whatever their true manner of death, here is the final tally of those who died around her:
Total number Number died
Husbands 4 3
Children 13 11
by previous marriage 7 5
Boyfriends 2 1
She is widely credited with the murder of all 21 individuals, but the number could be much higher or much lower. The moral of the story is, if you want to be a serial killer and not get caught until you're good and ready to be caught . . . time travel.