The story of Hannah Jones/de Chastaigne, the protagonist of The It Girl, unfolds through limited third-person narration. The narrative alternates between Hannah’s first year at Oxford University’s Pelham College and 10 years later in Edinburgh, Scotland, where Hannah lives and works. At Oxford, her discovery of her suitemate, April Coutts-Cliveden, strangled to death in their shared dorm room drastically changes the course of Hannah’s life. She believes that she contributed to the conviction of an innocent man, John Neville, for April’s murder. Guilt drives her actions as she investigates the night of April’s murder and the events leading up to it.

Intelligent and ambitious, Hannah achieves top marks while studying English literature. She values her relationships with her close friends, with whom she feels loyal and protective. Hannah comes from a lower socioeconomic class than most of her friends at Oxford. While self-conscious about her humble upbringing, Hannah recognizes she has had less coddling than her elitist peers. Hannah feels compelled to change her identity to be more like them:

She, Hannah, could reinvent herself here. Okay, she wasn’t as spiky or witty as Emily, or as cheeky and sarcastic as Ryan. But she could be someone else.