“Insanity runs in my family; it practically gallops.” That’s what Cary Grant famously declares in the 1944 movie Arsenic and Old Lace, based on the hit Broadway play. The macabre comedy, set on Halloween, followed the discovery by Grant’s character that his aunts had secretly been murdering renters at their boarding house. It’s a pretty grim subject for a comedy, especially considering that it was inspired by real events.

While working on Arsenic and Old Lace, playwright Joseph Kesselring traveled to Connecticut to examine court documents relating to Amy Archer-Gilligan, a convicted murderer who had run a boarding house for the elderly. Sixty-six people died at that house between 1908 and 1916. When investigators exhumed five of the bodies—including her second husband’s—autopsies revealed they had been poisoned with arsenic or strychnine.

Amy Archer-Gilligan and her first husband, James Archer, opened their small nursing home-boarding house in Windsor, Connecticut around 1907 or 1908. The Archer Home for Elderly People and Chronic Invalids typically had fewer than 10 boarders at a time; and understandably, there were some deaths among the elderly tenants. The first one was in 1908 and the second was in 1909. But after that, there was a dramatic increase. Between 1910 and 1916, there were 64 more deaths at the Archer Home.

One of the earliest deaths at Archer Home was Amy’s husband, James, who died in 1910 at age 50 (Amy may have been in her late 30s or early 40s). The cause of death at the time was Bright's disease, an older medical term referring to kidney diseases; and as far as we know, that may have been what it was. Amy married her second husband, Michael Gilligan, in late 1913. He died just three months later at age 56, with the cause of death recorded as valvular heart disease and “acute bilious attack”—i.e., digestion or stomach problems.

This time, her husband’s death seemed more suspicious. Though he was a widower with sons, his will left his entire estate to Amy. And he wasn’t the only person whose death seemed to benefit her. Boarders could choose to pay Amy either a weekly rate or a one-time $1,000 fee for lifetime care, and some of her boarders seemed to die suddenly after either paying her a lifetime fee or signing over some amount of money to her.

By the time her second husband died in February 1914, people in town (and boarders a the Archer Home) had already began to notice that the death rate there was suspiciously high. Still, it wasn’t until another boarder died suddenly a few months later, in May 1914, that anyone would begin to get to the bottom of what was going on.

That month, a 61-year-old boarder named Franklin Andrews died. The recorded cause of death was “gastric ulcers.” But when his sister, Nellie Pierce, was cleaning out his things, she found some correspondence between her brother and Amy, in which Amy seemed to be pressuring him for money; so she contacted the state attorney and the Hartford Courant.

Reporters at the Courant began to investigate the Archer House deaths. Carlan Goslee, who wrote obituaries for residents of Windsor, had already noticed the frequent deaths at Archer House, and had previously discovered from a Windsor drug store that Amy had purchased arsenic multiple times, supposedly to kill rats and bedbugs.

Courant reporters began reexamining death certificates and noticed that many of the boarders seemed to experience sudden deaths and/or stomach problems. They also compared the rates of death at the boarding house with those of other elder care homes, noting that the rate of death at the Archer House was much higher.

These discoveries prompted a state investigation in which authorities exhumed the bodies of five people who’d died in the boarding house. At the time, embalmers often used arsenic when preparing a body, so its presence in a corpse’s system wouldn’t necessarily indicate poisoning. But upon examination, investigators found that Franklin Andrew’s stomach contained enough arsenic to kill several people, strongly indicating that someone had poisoned him.

The other four bodies—Alice Gowdy, Charles Smith, Maude Howard Lynch and Amy’s second husband, Michael Gilligan—also showed signs of arsenic or strychnine poisoning. In May 1916, police arrested Amy Archer-Gilligan. Although they charged her with all five deaths, she only went to trial for Franklin Andrew’s death.

The next year, a jury convicted her of first-degree murder and sentenced her to death. Her lawyer appealed, and in 1919 she received a new trial, in which she pleaded insanity. This time, she was convicted of second-degree murder and sentenced to life in prison. In 1924, the state transferred her to the Connecticut General Hospital for the Insane in Middletown, where she remained until her death in 1962.

One of the immediate impacts of Amy Archer-Gilligan’s arrest and trial was on Connecticut’s standards for elderly care. In 1917, the state introduced a bill requiring the state licensing of elder care facilities, which now had to receive inspections and submit annual death reports.

The story of the Archer House murders also caught the attention of playwright Joseph Kesselring, who was in his early teens when Amy Archer-Gilligan was arrested and tried. Years later, Kesserling reached out to Hugh Alcorn, the attorney for Hartford County who had prosecuted Archer-Gilligan. Alcorn gave him access to court documents relating to her case.

When Arsenic and Old Lace opened on Broadway in 1941, Alcorn attended a show but reportedly didn’t like it. However, the play was a huge success, leading Frank Capra to release a film adaptation in 1944. Nearly a century later, many consider the film to be a Halloween classic—though they may not realize it was inspired by real, horrific events.