Let’s return now to the Baztan Valley, Navarre, the cloud-and-fog shrouded north of Spain, where detective Amaia Salazar must wrap up her toughest, most gruesome and most personal murder case.

“Offering to the Storm” finishes of the “Baztan Trilogy” based on the fiction of Dolores Redondo. We’ve followed conflicted, conspiracy-minded and dogged Detective Chief Salazar (Marta Etura) through her days as as “The Invisible Guardian, ” a sleuth pondering “The Legacy of the Bones.”Now, with everybody else convinced her cult leader mom died at the end of “Bones,” she must uncover the truth about Mom and her baby-sacrificing Spaniards once and for all.

This trilogy — Spain’s answer to “The Girl with the Dragon Tattoo” (long, lurid, a cinematic “page-turner”) — is about dead babies. And as the final installment begins with an infant being smothered in the crib, it won’t be for everybody.

It’s a beautifully gloomy, chatty mystery-thriller that’s always on its feet. Amaia is often on the run, chasing down the baby-killer in that first scene (Iñigo de la Iglesia), who mumbles “I have to finish this, I MUST finish this” (in Spanish or subtitled into English, or in dubbed English, if you prefer) as he’s caught.

Amaia tracks down her Hannibal Lecter, Dr. Berasategui (Álvaro Cervantes), a cult leader she caught in the last film, in prison where his threats are laced with clues.

She dashes from graveyards to morgues, questions the priest (Imanol Arias) who provides hints even as he tries to distance the Church from the crimes.

“Witchcraft is not Satanism,” he explains. “Insulting God is not the object!”

And she copes with homelife, where American husband James (Benn Northover) does most of the childcare of their new infant and gripes that she’s compulsive about her job.

Her sisters would agree with that. They’re ready to have Mom’s funeral, but damn if Amaia is going to accept that she’s dead without finding the old witch’s body.

Somehow, through all this running about, crossing into France to dig up old graves, trying to investigate “every mystery baby death in the past five years,” wearing out her staff as she drives through rain and snow, trying to get to that next witness/prisoner before their timely “suicide,” Amaia has time for a side-piece.

Ah, España!  They may have given up their siesta in the rainy north. But not bed-hopping.

Etura has made her career with this trilogy, and handles the cop patter and voluminous dialogue and emotional scenes with skill. The threats turn more and more personal in the story, in that “No one can protect you from Them” sense, and Etura sheds her poker-faced cop visage now and again.

But she still makes Amaia more interesting than compelling.

The story is so exposition-heavy that we’re getting new wrinkles, new trains of thought and lines of inquiry, right up to the end. That preserves the “twists,” but there aren’t nearly enough of those to justify the film’s gasping 140 minute sprint.

The best scene is the Navarre version of that American thriller staple, the police officer’s funeral. No bagpipes (a cliche of American cop movies), but moving nevertheless.

The most interesting new character for the finale is a grief-stricken, raging mother of a victim, Yolanda. Marta Larralde does more to get across the REAL stakes here — a conspiracy reaching high and far, going back decades, fanatics who have bought into monstrous rituals — than any other actor or character.

We never really get the “why” or “to what end,” though. It’s a conspiracy to preserve a cover-up, not a means to wealth and power?

Or…IS it?

Not exactly the sort of question you want hanging over a trilogy that’s eaten up close to seven hours of your Netflixing time, but that’s part and parcel of the whole “page turner” label. This page-turner trilogy was always better at eating up your time than filling it.

MPAA Rating: TV-MA, violence, nudity, profanity

Cast: Marta Etura, Leonardo Sbaraglia, Álvaro Cervantes, Marta Larralde, Imanol Arias and Benn Northover.

Credits: Directed by Fernando González Molina, script by Luiso Berdejo, based on the Dolores Redondo.  A Netflix release.

Running time: 2:19