"Splice" is a surprising sci-fi movie that raises more unsettling issues than you'd expect — it keeps raising new ones past the point where you'd think the filmmakers would have run out of them.

The picture seems like a simple Frankenstein tale at the outset. Clive (Adrien Brody) and Elsa (Sarah Polley) are two hotshot genetic engineers (and lovers) who've earned their reputations by splicing animal DNA to create strange new creatures to produce new proteins that can be patented for medical use. But when they approach the pharmaceutical company that funds their work with a proposal to add human DNA into the mix, the company, fearing public outrage, forbids them to do it. So Clive and Elsa decide to secretly create a human-animal hybrid on their own.

The Frankenstein template is frankly acknowledged by director and co-writer Vincenzo Natali ("Cube"). The main characters' names are a cute nod to Colin Clive and Elsa Lanchester, the stars of the 1935 "Bride of Frankenstein," and at one point in this film someone actually shouts — like Colin Clive in the previous 1931 "Frankenstein" — "It's alive!" But Natali follows the traditional nightmare premise — mere humans playing God in a quest to create life — into morally complex areas, from the deluded hubris of such a quest to issues of nature versus nurture, the sanctity of life versus the seemingly justifiable need to terminate it, and — most creepily — interspecies sexual attraction.

Things start going wrong early on, when Clive and Elsa unveil their latest animal creations — two big slug-like entities they've nicknamed Fred and Ginger — at a meeting of the pharmaceutical company's shareholders. Unbeknown to their creators, these grotesque creatures have suddenly mutated, and soon, the shareholders are splattered with blood (or whatever) and possibly reconsidering their investment strategies.

Back in the couple's lab, Elsa keeps pushing for the human-animal DNA mix — if they don't do it, she says, citing the default scientific rationale, somebody else will (and will reap all the glory ... and the patents). Clive is reluctant, but he finally agrees to press the fusion button, and soon there's a bizarre new resident in their outsize laboratory incubator — a being that starts evolving toward maturity at breathtaking speed.

Here, the movie's sophisticated visual effects — a blend of traditional prosthetics and digital manipulation, imaginatively engaging without waving their price tags at us — begin to unfold. The new half-human creature is female, which is reassuringly familiar; but it also has birdlike, backward-bent legs; wide, weird eyes; and a long tail with (as we soon see) a retractable spike at its tip. Elsa, who has previously rejected Clive's suggestions that they consider having children, feels her maternal feelings emerging, and is soon dressing the hyperactive homunculus in girlish frocks and calling it "sweetie." Not for long, though.

This early version of Dren, as Elsa names her, is played by little Abigail Chu. Then, as Dren swiftly matures into a teenager (giving a whole new meaning to "teen alienation"), a little-known and highly acrobatic French actress, Delphine Chanéac, steps into the role; and as good as the other actors in the film are (especially Polley, who once again demonstrates an eloquent ability to convey complex thought without words), it's Chanéac, with her otherworldly face morphing between vulnerability and menace, who becomes the star of the show.

It would be wrong to give away any more of this beguiling movie, which startles us at just about every turn. There are clear echoes of "Alien" and early David Lynch imagery; and cinematographer Tetsuo Nagata (who also shot "Micmacs" and "La Vie en Rose") gives some of the scenes a sleek chill that recalls the David Cronenberg of "Videodrome" and "Crash." But while the picture is itself a fusion, its recognizable influences are fashioned into something new. It leaves us to puzzle out our own moral conclusions, but its central message is encapsulated in a nervous exchange between Elsa and Clive, as their experiment begins spinning out of control. Trying to fathom Dren's increasingly alarming behavior, Elsa says, "None of her animal components have predatory characteristics." To which Clive replies, "Well, there's the human element."

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