Instinct (1999)

Within the stark confines of a penitentiary for the criminally insane, Dr. Theo Caulder, a psychiatrist of keen intellect and burning ambition, finds himself face to face with Ethan Powell, a profoundly disturbed anthropologist. Driven by a thirst for understanding, Caulder embarks on a perilous journey into the depths of Powell’s fractured psyche. This quest for knowledge soon transforms into a high-stakes gamble, pushing Caulder to the precipice of self-destruction as he confronts the unsettling truth behind the madman's inexplicable behavior. His relentless pursuit of answers will test the very limits of his sanity.