Instinct (1999)

"Nothing is more savage than civilization."

In a prison for the criminally insane, deranged anthropologist Ethan Powell is set to be examined by a bright young psychiatrist, Theo Caulder. Driven by ambition and a hunger for the truth, Caulder will eventually risk everything—even put his very life on the line—in a harrowing attempt to understand the bizarre actions of this madman.