Forgive me if I start screaming,” I tell those at the screening of “Insidious: The Last Key.”

I was right to give a warning. Because I did end up screaming, just like I did while watching the previous “Insidious” films. But there was something “Insidious: The Last Key” did that the others didn’t: it made me cry.

“The Last Key,” the fourth “Insidious” film, is the most layered and textured of the franchise.

“Insidious: The Last Key” is written by “Saw” and “Insidious” cocreator Leigh Whannell and produced by Jason Blum (“The Purge” series, “Get Out,” “Split”), Oren Peli (“Paranormal Activity”) and cocreator James Wan (“The Conjuring,” “Furious 7”). New to the series is director Adam Robitel (“The Taking of Deborah Logan”).

Dr. Elise Rainier (played by the incredible Lin Shaye), psychic, clairvoyant and demonologist, who we have gotten to know since the first “Insidious” film in 2010, takes center stage in “The Last Key.” “It’s been fascinating to watch Lin’s evolution as Elise over this series,” says Jason.

In the first “Insidious” film, Elise and her sidekicks Tucker (Angus Sampson) and Specs (Leigh) help Josh and Renai Lambert bring their son Dalton back from The Further, which Elise describes as “a world far beyond our own,” where dark spirits roam.

“Insidious: Chapter 2” reunites the Lamberts with Elise, who is in The Further.

“Insidious: Chapter 3” goes back in time to a period in Elise’s life before the Lamberts. In this chapter, Quinn Brenner, a young teen still reeling from grief, seeks Elise’s help after her attempts to contact her mother in the afterlife goes horrifically wrong.

Although released last, chronologically, “The Last Key” is the second in the series and picks up where “Insidious: Chapter 3,” the prequel to the first “Insidious film,” leaves off.

But “The Last Key” works as a stand-alone film, too—seeing the trilogy isn’t a requirement for you to enjoy it.

Call for help

It’s 2010 in California and Elise is now living and working with Specs and Tucker. A call for help from a man named Ted Garza forces her to face the horrors of her past. Ted lives at 414 Apple Tree Lane—Elise’s childhood home. “I don’t have memories from that place, I have scars,” she says.

Through flashbacks, “The Last Key” takes us to Five Keys, New Mexico, in 1953 where a young Elise is living with her family.

She already has the ability to communicate with the dead at that early age—a gift she seems to have been born with—but she is also plagued by other horrors, including a father who cannot accept her special skills and punishes her for them. “My father tried to beat it out of me,” Elise says. But he clearly didn’t succeed as Elise spends her lifetime helping those plagued by paranormal entities. “This is an origin story,” says producer Jason.  “It shows how Elise came to be, and how she got her special powers.”

Like purgatory

Elise’s trip back to her childhood home is fraught with danger and leads her back to The Further. “It’s like purgatory. It’s the realm of the dead… all of the tortured souls that haven’t quite finished with their business on Earth reside in this realm,” says Leigh.

Adult Elise comes face to face with Key Face, a demon she unleashed into the world as a kid. Key Face, who feeds on misery and has the power to manipulate the living, has been wreaking havoc on countless people’s lives for decades and Elise has to stop him.

“He has skeleton keys for fingers and uses those skeleton keys to kill people,” said Jason.

“There’s a lot of symbolism with this particular demon,” says Leigh. “The town that Elise grew up in in New Mexico is called Five Keys.  She also grew up on the grounds of a prison. Her father was the assistant warden.  All these things that Elise has locked away, this demon has the power to lock and unlock.  By confronting this demon, Elise confronts her own past and her own locked doors—the things she’s shut out of her life.”

Lin, clearly the heart of the franchise, shines in her complex portrayal of Elise.

Light moments

“Insidious: The Last Key” isn’t all darkness and scares. Like the previous films, it is punctuated by moments of lightness, entertaining bits, usually courtesy of Specs and Tucker, that offer a breather from the tension. “There’s a certain fun to the ‘Insidious’ films—a wink at the audience,” Jason says.

Fun too is getting glimpses of the other ‘Insidious’ films, witnessing the filmmakers play with foreshadowing, and figuring out how the new film fits in with the old ones. “It’s the trickiest to make it look like we intended it that way when really it’s an afterthought. How can we make this film lock in to this movie? I do enjoy doing that and if the audience responds the way you did by enjoying it then I’m so happy because I really reverse engineer each film,” says Leigh.

“The Last Key” explores themes of fear and fortitude, family and forgiveness and different kinds of horror, living and dead, paranormal and not. It offers surprising twists and turns, with the past and present colliding for a terrifying and emotional ride.

Columbia Pictures’ “Insidious: The Last Key” opens nationwide on Jan. 17.