“An eccentric firearm heiress believes she is haunted by the souls of people killed by the Winchester repeating rifle.”

It’s the description of Helen Mirren’s newest film, Winchester, but the horror movie is rooted in a truth that some believe is even scarier.

Mirren plays Sarah Winchester, who came into the considerable fortune after the death of her husband, William Wirt Winchester, in 1881.

The couple’s only child died in infancy, leaving Sarah to inherit her husband’s $20 million estate — equivalent to more than $507 million in 2017 — and nearly 50 percent holding of the Winchester Repeating Arms Company, of which he was treasurer.

The company invented the revolutionary repeating firearm called the Henry rifle and later created the Enfield and the Browning automatic rifle for the British army.

Her share of the company gave her an income of $1,000 a day, or about $25,000 per day by today's standards.

But she sunk most of her fortune into a behemoth of a home now known as the Winchester Mystery House, which is the inspiration of the 2018 horror film.

In 1886, Winchester moved with her sister and niece from Connecticut and purchased an eight-room farmhouse that stood on 161 acres of land in what is now San Jose, Calif., according to reports.

She immediately began renovating the home, spending nearly four decades transforming it into a 24,000-square-foot Queen Anne Victorian mansion that once stood seven stories tall.

No master building plan of the home existed, but it is believed it had 161 rooms, including 40 bedrooms, six kitchens and two ballrooms, along with many oddities very few could explain.

Staircases leading nowhere, doors that open into walls and windows that look into other walls all were a part of the home’s reported constant construction and the serving staff’s need to have maps on hand.

“There is no question that the Winchester Mystery House has taken its place as one of the most peculiar homes in the world,” the website for the house, now a landmark, notes. “A mansion so wrapped in legend, lore and continued fascination by the public that its moniker of ‘Winchester Mystery House’ seems completely justified.”

It’s not clear why the heiress was compelled to build such a labyrinth of a home, but legend has it she believed a medium who warned that she and her family was cursed by the victims of rifles made by Winchester Repeating Arms Co.

And the ghosts of those victims would only be satisfied if Winchester built them a home, spawning the large-scale and constant construction, according to legend.

Winchester supposedly slept in a different bedroom each night, avoiding routine to confuse any ghosts that may wish to do her harm.

Winchester was 82 when she died in 1922, and only then did construction on her home cease.

The house, which eventually stood at four stories after an earthquake caused considerable damage, was transformed into a tourist attraction that's still open to this day.

“Whether one believes in spirits or not, there’s no denying the presence of someone (or something) here at Winchester Mystery House,” the home’s website notes. “Numerous visitors, tour guides and employees have experienced strange phenomenon, including capturing orbs and images in photographs and video.”

Winchester opens in theaters on Friday.

RELATED STORIES

'Amityville Horror' Home Goes on the Market With No Mention of 1974 Murders of 6 People Inside

Amelia Earhart Mystery Solved? Photo May Be Proof Iconic Aviator Survived Crash, Was Taken Prisoner

The Mystery of the Flashing Lights at the White House