When you're an adult, Bloody Mary is something you order in a bar. As a child, it's a game you played with cousins and friends at sleepovers, a ritual in which you stare at a mirror and call out the name of Bloody Mary three times in order to summon an apparition who will apparently do horrible things to the summoner.

Of course, mirrors hold a special place in the Enchanted Objects Department. The old superstition about turning mirrors to the wall or covering them up after a person has died, to prevent the spirit of the deceased from seeing its own reflection and becoming confused, may differ only slightly from the Bloody Mary folk story in that the spirit is summoned because someone forgot to cover a mirror, as opposed to being purposefully called up. Urban legend or ritual, it's a ghost story. And a cautionary one.

Writer/director Mike Flanagan's take on evil mirrors is a pretty intelligent concept, actually. Siblings Kaylie (Karen Gillan) and Tim (Brenton Thwaites) must face off against an apparently malevolent reflective glass that they believe destroyed their family a decade earlier.

The story opens with Tim being released from a psychiatric hospital after a 10-year stay. Kaylie, who lived in foster care, went on to college and a personal mission: to destroy the mirror she believes is responsible for the death of not only their parents but a score of people, all of whom were driven to murder and suicide by whatever they saw in the glass. She tracks down the mirror and, after intercepting it before it can go up for auction, places it back in their childhood home. After setting up a ghost hunters' dream in their father's former office, which she intends to utilize to record what she believes is an "observable, predictable force" inside the mirror, she enlists Tim's help in attempting to document and then destroy this evil presence.

The movie gets by on restraint. Mirrors are a play on image, self and reality, and Flanagan doesn't put that metaphor down for a moment. It works, for the most part. Flanagan creates a strong atmosphere with hallucinatory camera work that plays constantly with visual boundaries and offers a number of fairly decent corner-of-eye surprises with well-done strange creaks, weird visual jolts and long tracking shots followed by macabre images. The ear-teasing soundtrack, loaded with deep, menacing bass whenever the action takes a turn for the dark, helps set the somber, haunting mood.

The only hitch is that the movie is so dark, so increasingly hopeless, that it's hard to stay connected, especially toward the (pretty creative) end, the bleakness having killed off a good bit of the entertainment value. But it's still headed directly for cult status, right up there with Ringu as one of the more intelligent reality-bending horror flicks.