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Four films in, the horror franchise "Insidious" deserves recognition for its unusual star, Lin Shaye. It isn't the character she plays — a psychic named Elise —that's noteworthy, but her age.

Shaye is 74, which makes Elise at least thrice the age of the baby sitters and camp counselors who traditionally serve as horror-film heroines. And the filmmakers respect that by allowing her more dignity than those girls.

She never has to seduce the audience by taking a shower or run from a killer wearing only her bikini. Elise is as much the hunter as the hunted, a dogged ghostbuster who's always first through the darkened doorway with a flashlight. Good for Shaye, enjoying a terrific run after a 40-year film career. And good for this teen-targeted franchise for casting her time and again.

If only the movies were better. The early installments felt awfully slapdash, with crude effects and even cruder acting (even though co-creators James Wan and Leigh Whannell were established professionals who had given us the "Saw" franchise). "Insidious: The Last Key" is a step up, boasting some clever scares from new director Adam Robitel, a reasonably impressive demon-creature and, finally, something like an original story from Whannell.

In this origin-story episode, Elise — Shaye plays her like a more-earnest, less-puckish version of Angela Lansbury in "Murder, She Wrote" — is called upon to cleanse the childhood home in New Mexico where she developed her psychic gifts. It's also where she endured years of abuse from her father (Josh Stewart). As Elise tries to help the home's new owner, a roughneck named Garza (Kirk Acevedo), she discovers a secret about her family.

That's relatively deep stuff for this franchise, which until now has been content to copy 1982's "Poltergeist." The execution can be a bit clumsy, especially the attempts at comic relief by Elise's assistants, the swaggering Tucker (Angus Sampson) and nerdy Specks (Whannell). The best creation here is a demon whose fingers, shaped like skeleton keys, can lock the scream in your throat.

The title of "Insidious: The Last Key" suggests an end to the franchise, which would be too bad. It feels like it's just getting started.