It's the story of a woman who is forced to be a drug carrier, and I do mean forced. Five people are kidnapped, including Lucy, and a plastic baggie filled with a strange drug is inserted in their stomachs. They are then forced on planes to Paris, Rome, etc. to be met by drug couriers on the other end.
The drug isn't your typical dealer's favorite high. It's a wildly powerful substance that babies use to form their brains in the womb. But it's available only in tiny quantities. However, an enterprising criminal learned how to synthesize a relatively large quantity -- and that is what was placed into the victims' stomachs. Okay, that sets the scene.
Lucy, unfortunately (or fortunately, depending on how you look at it) was in the custody of monstrous, women-hating thugs as she awaited transport on the plane. One of them tried to rape her and ended up kicking her in her stomach -- and perforating the bag. It's at this point that the movie really begins.
The drug has the effect of opening up the mind. The movie is built on the myth that says humans only utilize 10% of their brain-power. This is totally false but hey, it's only a movie. So as the drug courses through Lucy's system, she begins to evolve, quickly and madly.
The movie veers into fights, with Lucy able to lift people into the air with the power of her mind. She can do lots of other tricks, too. And all the while, her brain advances. At the climax of the movie, she reaches the point where she is utilizing 100% of her brain.
That's all I'll reveal, but I have to say I found the entire movie, and especially the conclusion, to be wildly wonderful and entertaining. The only reason some viewers gave it a low rating, I suspect, is that Lucy doesn't continue to fight people and blow things up for the entire movie. At a certain point, it becomes much more intellectual -- and that's the point at which you lose American viewers. Fight scenes and car chases? Love it. But intellectual stuff? Americans say "get me outa here!"
It's a fabulous movie. If you've seen it, chime in. As for me, I plan to watch it a few more times. You see, what Lucy discovers is in keeping with what I believe to be the true nature of reality. I won't say another word.