What happens to Mark in I Am Number Four?

In I am Number Four by Pittacus Lore, Mark James starts off as the school bully. He is Sarah's ex-boyfriend and jealous of John, which leads him to bully and fight John. By the end of the novel, he learns of John's powers and fights alongside him.
In the Battle of Paradise High School, Mark fights the Mogadorians. He saves Henri's life. John tells him to hide with Sarah and protect her. At the end, when John is unconscious, Mark brings him out of the school and to the motel.
John leaves Paradise, along with Six and Sam. Mark stays in Paradise. In 2014, Pittacus Lore published a book called I Am Number Four: The Lost Files: Return To Paradise. This companion novella explores life for Mark following the battle and after learning aliens exist.