Stevie is a 16-year-old girl, a first-year student at Ellingham Academy, and the main protagonist of Truly Devious. Stevie loves everything related to crime and mystery, and she dreams of being a detective like Sherlock Holmes or Hercule Poirot. When Stevie first arrives at Ellingham Academy, she is full of ambition and a dream to solve the cold case of the Ellingham murders that took place over 80 years ago. However, as the school year begins, Stevie finds herself facing down a new mystery that hits closer to home, and she believes that only she can crack the case of what happened to YouTube star Hayes Major.

Stevie has a complicated relationship with her parents. In Chapter 1, Stevie and her parents make the long journey to Ellingham Academy, and Johnson paints a clear picture of a family wrought with tension. Stevie believes that her parents think she is strange, and when she makes her usual jokes or playful commentary, she imagines them thinking something along the lines of “We kind of wanted the going-out, shopping, prom-going type, and we got this weird, creepy one, and we love it but what is it talking about, ever?” (24).