Nine infant aliens, who closely resemble humans flee from their home planet Lorien, to hide on Earth. An invading species, the Mogadorians who have destroyed their planet follows them to Earth to hunt them down. Each of the nine aliens is given a guardian and they will develop superhuman powers as they grew up. They are each assigned a number and these last children of Lorien can only be killed in the sequence of their numbers. Number Four (Alex Pettyfer), also named John Smith moves to Paradise, Ohio, disguised as an American high school student. He befriended a girl named Sarah (Dianna Agron), a sweet Midwesterner who is a photographer. After being on the run his whole life, Number Four falls in love and now has something to stand up and fight for.