Lucy is an American studying in Taipei, Taiwan and is tricked into working as a drug mule by her new boyfriend Richard for a South Korean kkangpae and drug lord. Lucy delivers a briefcase to Mr. Jang containing four packets of CPH4, a highly valuable synthetic drug. After bearing witness to Richard getting shot and killed, she is captured and a bag of the drug is forcibly sewn into her abdomen in order to transport the drug to Europe. While in captivity, she is kicked in the stomach, breaking the bag and releasing a large quantity of the drug into her system. She acquires increasingly enhanced physical and mental capabilities, such as telepathy, telekinesis, mental time travel, and the ability to feel no pain. She also becomes both ruthless and emotionless. Using her new abilities, she kills her captors and escapes. Lucy travels to the nearby Tri-Service General Hospital to get the bag of drugs removed from her abdomen. She is told by the operating doctor that natural CPH4 is produced in tiny quantities by pregnant women during their sixth week of pregnancy to provide fetuses with the energy to develop. Growing heightened physical and mental abilities, Lucy returns to Mr. Jang's hotel, kills his bodyguards, assaults him, and telepathically extracts the locations of the three remaining drug mules from his brain. Lucy begins researching her condition and contacts scientist Samuel Norman whose research may be the key to saving her. After Lucy speaks with Norman (and provides proof of her developed abilities) she flies to Paris and contacts local police captain Pierre Del Rio to help her find the remaining three packets of the drug. During the flight, she starts to disintegrate as her cells destabilize from consuming a sip of champagne. To stave off her disintegration Lucy ingests more of the drug. With the help of Del Rio, Lucy is able to recover the rest of the drugs. Meeting Norman and his colleagues, she agrees to share with them everything she knows. In the professor's lab, Lucy discusses the nature of time and life and how people's humanity distorts their perceptions. At her urging, she is intravenously injected with the contents of all three remaining bags of CPH4. Her body changes into a black substance that begins spreading over computers and other electronic objects in the lab transforming them all into one next-generation supercomputer. She mentally begins a spacetime journey into the past, eventually reaching the oldest discovered ancestor of mankind, Lucy. She shares a quiet moment with australopithecus Lucy and the two touch fingertips, she then goes all the way to the beginning of time and witnesses the Big Bang. Meanwhile, Jang enters the lab and points a gun at Lucy's head. He shoots, but by that point Lucy has reached 100% of her brain capacity and promptly disappears, moving into the spacetime continuum. Only her clothes and the black supercomputer are left behind. Del Rio enters and fatally shoots Jang. Norman takes a black flash drive offered by the supercomputer, after which it too disintegrates. Del Rio asks Norman where Lucy is, immediately after which Del Rio's cell phone sounds and he sees a text message: "I am everywhere." Lucy's voice is heard stating "Life was given to us a billion years ago. Now you know what to do with it."