A brilliant new forensic chemist joins the BAU, hiding a dangerous past, a new identity, and the faint Slavic accent she can’t fully erase. Trained to notice every detail, the BAU quickly realizes there’s more to her than her résumé reveals — especially Spencer Reid, whose curiosity uncovers cracks in the story she worked years to perfect. As old threats resurface, the truth she fought to bury closes in, and the BAU must decide whether to expose her or protect the person she’s become.