Sarah Hart

Sarah Hart is the only one person at John's new school in Ohio, other than Sam, that offered to be close with him.

John and Sarah officially became a couple after the Haunted Hayride in book one.

Sarah is portrayed as an intelligent and extremely beautiful teenage girl with straight blond hair past her shoulders, ivory skin, high cheekbones, and soft blue eyes. Originally a cheerleader, she dated Mark, John's rival at school. After her parents realized what a bad influence Mark was, they sent her away for the summer.

Upon her return, inspired by the sights she had seen during her time away, she quit the cheerleading squad and broke up with Mark. She is passionate about photography and animals. She became friends with John when they met and soon started a relationship. After John saves her from a house fire, she realizes he is not human and John is then compelled to tell her the truth. Despite knowing that he is not human, Sarah finds herself deeply in love with John and confesses it to him, which he does the same. After the Mogadorians try to kill John, he leaves her, unwillingly, at the end of I Am Number Four, promising to come back .

In Book Two,  The Power of Six, Sarah appears only once (but is still mentioned throughout the book). While passing through Paradise, Four, along with Sam, contacts her and they meet in a park. Although they start their meeting with joy, Sarah starts to tell Four to turn himself in and checks her mobile phone several times, though she claims it is just a text from a friend. It soon becomes clear that Sarah is jealous about Four's relationship with Six. They have an argument, leaving Sarah in tears. The FBI suddenly appear, Sarah is whisked away, and Sam and Four are arrested. It was implied that Sarah is the one who betrays Four and reveals his presence to the FBI, by communicating with the police via her phone.

In Book Three, The Rise of Nine, it is explained that Sarah did not betray John and was captured by the Mogadorians after the FBI took him away. They drugged her and forced her to repeat whole conversations word for word. She has been held captive by the Mogadorians and even meets up with Six, who was also captured. Sarah and Six become close friends. After John, Nine, Eight, Seven, and Ten find her, John and Sarah have a brief moment with each other before they battle Setrákus Ra, who is holding Six captive. She is currently with the rest of the Garde (except Number Five) looking for a way out of the government base.

In Book Four, The Fall of Five, she is still with the group when Sam joins them and spends a lot of her time with John. Despite Four's protectiveness, she learns to shoot in order to protect herself. While Six, Five, Eight, and Nine all leave to get Five's Chest, she stays behind with Sam and his father, Malcolm, to take care of John, who was pulled into a coma-state along with Ella. When the Mogadorians attack their hideout, she helps to fight back, but despite her and Sam's best efforts, Ella is captured and Malcolm Goode is almost killed. She is last seen helping Sam and Malcolm escape, while John stays behind to find his own way out.