How much of a movie that is “Based on a True Story” has to be, well, based on a true story?

Is it enough that a ghost movie that is marketed as portraying actual events be creepy, or does it owe its audience at least some degree of veracity? If you think being occasionally scary is enough, you might enjoy “The Haunting in Connecticut.” If you prefer your ghostly yarns without a side order of bullshit, I suggest you order from a different menu.

Virginia Madsen, (“Sideways”) stars as Sara Campbell, a middle-class mom whose teenage son Matt (Kyle Gallner) is dying of cancer. In order to be closer to the hospital where Matt is receiving experimental treatment, Sarah moves with the kids to a house in Goatswood, Conn. — sounds creepy already, right?

Turns out the rent is cheap because the place used to be a funeral home, and a locked room in the basement still contains the implements of the mortician’s trade. Matt decides to make the basement his bedroom and soon he is being stalked and haunted by visions of a boy who used to live in the house. The kid was a powerful medium who, under the direction of the undertaker/black magician, conducted séances. I suspect you can fill in the spooky part of the plot from here.

Elias Koteas (“Zodiac”) co-stars as a local minister and resident expert on ghosts who is also dying of cancer. See, the cancer brings people closer to death which allows them to see spirits that healthy folks can’t. He quickly figures out that the late mortician experimented with necromancy, a particularly nasty form of magic that requires dead bodies to work.

First-time feature director Peter Cornwell does a nice job is establishing and maintaining an aura of the weird and mysterious, at least until the script by Adam Simon and Tim Metcalfe reaches its fever pitch in act three, bringing the thing mighty close to self-parody.

The movie’s problem with truth is this: None of this stuff ever happened. The house was actually rented by the Snedeker family. The adults claimed that they were raped repeatedly by invisible demons, among other less extravagant stories. Despite this, they lived in the place for two years. Mmm … demon sex!

The whole yarn was debunked in 1992, but not before it was turned into an Amityville-type book. Oh yeah, the idea for writing a book about the affair came from a husband and wife team of demonologists, the same pair who “investigated” the house in Amityville. If it looks like a duck and waddles like a duck, odds are it’s a quack.

Most viewers won’t care about the lack of truth in this “true story,” but please don’t leave the theater thinking that every little bump you hear in the night is a murder victim seeking revenge or Aunt Tillie trying to let you know where she buried her fortune. It’s fiction, folks. You know — the stuff people make up. If storytellers can’t make it sound stranger than truth, they’re not very good at their job.