Luc Besson’s mildly entertaining “Lucy” is part-B action movie and part-high-concept science fiction about the potential of the human brain. It stars the sexy, doe-eyed Scarlett Johansson as the titular character Lucy, a young, naïve American in China who gets caught up in some shady, underworld dealings.

Lucy gets selected as a drug mule for a new drug (a synthetic version of the drug CPH4, which allows someone to use more than 10 percent of their brain), and through certain circumstances, a large dose of it gets into her body. Before long, she’s able to harness up to 100 percent of her cranium.

Johansson — who’s been on a roll acting-wise of late, in films like “Under the Skin” and “Her” — gives a perfectly fine performance, though nothing spectacular.

It ranges from huffy and panicky (at the beginning) to robotic and wide-eyed. Johansson does a lot of intense staring because she’s super-smart and focused all the time. She does have moments of greatness, like when she’s trying to cope with her newfound abilities and understand them, while slowly losing her humanness.

And this is where “Lucy” is most intriguing. Besson’s screenplay addresses some extremely interesting concepts related to brainpower and human biology. Basically, the main theory he puts forth is — delivered by Morgan Freeman, whose talent is wasted as a brain scientist giving a Parisian university lecture — that in our current state as humans, we create obstacles for ourselves in the form of fear, pain, anxiety, etc., thereby limiting ourselves and our full potential.

Being exposed to this drug has caused Lucy to eliminate those obstacles, which is great on the one hand, but on the other, she loses her humanness. She can’t feel pain or fear — hence, Johansson’s robotic performance.

Unfortunately, as interesting as “Lucy” may be, Besson decides to wrap the picture in a derivative, B-movie blanket that smothers the picture’s potential to be truly memorable. Lucy essentially turns into another super-gal: She acquires fist-fighting skills and eventually gets so smart that she can control other humans and matter with her mind. And, of course, since this is about an illegal drug, there are a lot of generic Chinese gangsters and a forgettable French police officer who aids her.

Besson’s movie is a peculiar amalgamation of genres: There’s some “Jason Bourne” in there, along with “The Matrix” and a dash of “ The Tree of Life.” That Terrence Malick art film? Yep, that’s the one.

Not that there aren’t any mild, B-movie pleasures to still be found. At 89 minutes, “Lucy” doesn’t wear out its welcome, and Besson keeps the picture moving at a fast pace. Besson also has some fun with it, the overall tone switching from intense drama/action to sheer goofiness, such as the way Lucy casually and apathetically kills people or reads and comprehends hundreds of hours of research and data in a matter of seconds.

Consequently, this prevents the audience from really caring about any of the characters, but it also makes the movie fun in a pulpy-action-movie way. As it is, had the film taken itself completely serious, it would have been a bust.

Had Besson been more concerned with the intriguing themes involving brainpower and brain usage, instead of action-movie tropes, “Lucy” might have been great.

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