I could say that Lucy is a film about a woman conned into acting as a drug mule for some very disreputable men, but I'm not sure how accurate that is. The film is actually about the myth that people only use 10% of their brain's capacity and what might happen were we to tap into the other 90%. I think the fact that this myth has been debunked many times over is interesting as it brings up some questions about the amount of science needed in Science Fiction, but more on that in a bit.
As a film, Lucy is OK at best; it's certainly watchable if not fully enjoyable. Scarlett Johansson is wonderful as always, and she does a great job presenting Lucy's progress from a sweet, normal (whatever that means) girl to someone seemingly devoid of humanity or empathy. The suggestion that higher brain capacity and function leads to someone being less human instead of more is certainly interesting, though not very unique or original. Morgan Freeman is also a pleasure, but that's mostly because Freeman is always a pleasure. He does little more here than deliver exposition in his great Morgan Freeman voice. The film also features a diverse group of top billed actors, which is always commendable. But that's about where the compliments end. Spoilers to follow.
The film's cinematic problems include general plot hole and continuity struggles. Early on in her brain activation, the point is made that Lucy is becoming less and less human. The implication being she's starting to lose some basic human empathy. She quickly finds the man responsible for her current state. She effortlessly kills all of his guards, immobilizes him, uses her new telepathic powers to find out where all of the other drug mules were sent so she can start the process of hunting them down, and then she leaves him alive. Why? She has no problem killing the men working for him, and yet when she has this man (who is far worse than his little worker bees) at her mercy, she leaves him alive. The film offers no reasoning for this choice, so I'm left thinking that it happened because the plot required it. They would have been robbed of their big finish showdown sequence had she killed him early on. The movie is full of these head scratching moments.
But these storytelling problems are nothing compared to the films extremely faulty logic and science. I think there's a fair amount of balance that is expected from a Science Fiction film. If there's more fiction than science, I think audiences (or more specifically just me) will be capable of suspended disbelief and just going with it so long as the bad science doesn't ask more questions than it answers. When there's more science than fiction, you run the risk of the story being boring. For an example of this, read Michael Crichton's Jurassic Park which is far more interested in how dinosaurs might be made than it is in telling a story and, therefore, isn't near as good as it's film adaptation. Lucy falls into an odd space where it feels like the filmmakers are more interested in science than story and yet their science is horribly flawed and nonsensical.
Let's say for the moment that we were to suspend our disbelief about the 10% problem; that still doesn't explain why more brain function would in anyway alter the basic physiology of the human body. You can't think yourself into a new hair color just because you've got a bit more brain power. Octopus and Chameleon cells can do that, human bodies cannot and nothing the film posits suggests that that basic physiology would change. Likewise, the chances of the human body morphing into some weird goo to form a super computer is highly unlikely. The film doesn't intend on its viewers asking the questions of how or why Lucy is capable of doing the things she ends up doing. They fully expect you to take them at their word that this is what would happen. In doing so, it feels like the writers heard once that viewers will suspend disbelief but they never stuck around to find out the steps needed to ensure that would happen. I couldn't stop asking these questions and when the film refused to provide answers, I was left being pulled out of the narrative.
I seriously wanted to like Lucy. As a person who's been wanting a Black Widow film since the character was introduced back in Iron Man 2, I thought this might be a nice way to bridge the gap to that film. A female fronted action movie starring Black Widow herself that was successful might lead the people behind Marvel Studios to see just what they were missing by keeping her out of her own franchise. Instead we got a film that seems to want to walk in between genres and doesn't really do one or the other well.