John Muller, a recently paroled criminal, masterminds an elaborate casino heist which goes awry, leaving him on the run from both law enforcement and a vengeful gang. With every escape route rapidly closing, he assumes a new identity to evade capture, and his pursuit leads him to Dr. Bartok, a psychiatrist who bears an uncanny resemblance to him. Recognizing an opportunity to disappear, Muller meticulously studies every aspect of the doctor's life, planning to murder and replace him.

Muller’s transformation into Dr. Bartok involves altering his appearance and adopting the doctor’s characteristics. He ingratiates himself with Bartok’s surroundings, including his office staff and his complicated romantic interest, Evelyn Hahn. As Muller delves deeper into his new role, he finds that embodying another person is more challenging than he anticipated, with unforeseen complications and growing suspicions threatening to expose his deception. Tensions rise as Muller struggles to maintain his cover in a web of deceit where both danger and discovery lurk at every turn.