Girl Online tells the story of Penny Porter, a 15-year-old girl from Brighton who secretly writes a popular blog under the name Girl Online. Penny struggles with anxiety and panic attacks, especially after an embarrassing incident at school. When her family travels to New York for a wedding, she meets Noah, a charming musician, and falls in love with him. However, Noah is hiding a secret that could change everything. As Penny's online and real lives collide, she must learn to deal with friendship, love, fame, and self-confidence