The central premise of Lucy – that human beings only use 10 percent of their brain capacity – is, in and of itself, faulty and patently untrue. However, considering that the film in question is a sci-fi action thriller from writer/director Luc Besson (The Professional, The Fifth Element), viewers should expect to a certain suspension of disbelief going on. However, with such an intriguing idea at its core, the question remains whether Lucy takes full advantage of the storytelling potential it holds.

Scarlett Johansson stars as the title character, a young college student living in Taiwan. Minutes into the film, she falls in with drug lord Mr. Jang (Choi Min-sik of Oldboy fame) and is forced to smuggle an experimental drug, which accidentally enters her bloodstream. Before long, Lucy finds that the drug has literally mind-expanding effects on her. Her brain capacity expanding at a rapid pace, she must figure out how to control her developing powers and save her own life before the drug’s side effects prove fatal.

First of all, Johansson is dynamite in the role and proves once again that she is worthy of her own action franchise (such as the ongoing rumors about a spinoff Marvel film for her Black Widow character). Early on, she nails Lucy’s vulnerability and helplessness, and as the character begins to lose her humanity, her performance adjusts accordingly. Viewers can see the change in her face when fear and anxiety melt away, replaced only with a steely determination. In fact, the best scene in the film features nothing but a closeup on Johansson’s face as – feeling her emotions slipping away – she makes an impromptu phone call to her mother. It’s a powerful moment and  perhaps the one that best encapsulates the sad irony that increased power, at least according to this film, equates to more emotional detachment.

Likewise, Choi is spot-on perfect for the role of Jang, providing a menace and gravitas befitting an underworld kingpin. He and Johansson act as perfect counterpoints throughout the film, and in fact, find their roles reversed as the balance of power begins to shift. Less fortunate, however, are Amr Waked (Syriana) and Morgan Freeman. Both are wasted in flat supporting roles as the detective and scientist, respectively, who aid Lucy on her mission.

The first half of Lucy’s journey – from victim to full-on superhero – starts off strong. She develops impressive, though increasingly ludicrous, abilities, including many that are unrelated to one’s brainpower. Telekinesis, telepathy and agility are acceptable science fiction standards that make sense given Lucy‘s outlandish premise, but Besson extends the character over-the-top powers like inexplicable control over matter, electricity and time. It reaches a certain point where the film appears to spontaneously grant its lead character whatever abilities she needs to prove herself the unstoppable force it needs her to be.

If that wasn’t bad enough, the decline of Lucy’s humanity – so well portrayed early in the film (and exemplified during that excellent phone call scene) – essentially disappears in its second half. Emotionless and bland, the character goes around kicking ass without any threat to her, and as a result, the storyline fails to establish any stakes worth caring about. When a hero such as Lucy is essentially godlike, any measure of suspense is instantly deflated. This is precisely why all-powerful characters like Superman are difficult to create a compelling film around.

After it loses control of its ambitious sci-fi premise, Lucy even fails to work as an visually exciting action thriller. Because Johansson’s character can control her enemies and her environment effortlessly, there aren’t even any memorable fight scenes to speak of, save for one or two quick beats early on. Anyone interested in solely seeing Lucy for these can get just as much satisfaction from watching the film’s trailer and saving themselves the other 87 minutes.

Besson and his team ostensibly hoped to use Lucy‘s pseudo-scientific storyline as a launchpad for a thought-provoking adventure that challenged viewers to consider the possibilities that could be yielded by increased brain capacity. Unfortunately, the end result is far more likely to exercise moviegoers’ patience than their minds.

Rating: 2 out of 5

Lucy stars Scarlett Johansson, Morgan Freeman, Min-sik Choi and Amr Waked. It is directed by Luc Besson and is now in theaters.