Summer is 7 years old and goes to her first Christmas party, where she meets a surprisingly, nice 7 year old boy named Harry Styles. His piercing green eyes, straight-ear length, light brown hair and his charming personality sucked Summer right into him. When they meet each year at this one Christmas party, Harry always ends up dragging Summer underneath the mistletoe. Every single year Summer and Harry become closer and closer. But when Summer is 15 going on 16, Harry tells her at Christmas that he has entered the X-Factor. He asked her to come and she did. Once he made it through she was so proud. She told him she would see him at Christmas.Harry said he wouldn't forget. But he did. Summer goes to the party again;thinking she'd see Harry. But Summer is shocked when Harry's sister tells her Harry isn't there is because he was spending time with his girlfriend from the X-Factor. At Harry's girlfriend's house, Harry spots a mistletoe and remembers Summer, remembers their memories and remembers their kisses. Harry immediately leaves the party, to go see Summer but when he arrives Summer was no where in sight. So Harry does what he needs to do...he goes out to find The Girl Underneath the Mistletoe and brings her along with his journey of fame and fortune.