Shock Corridor (movie, 1963)

Determined to pull in the Pulitzer Prize, reporter Johnny Barrett will go to any length necessary to win the coveted award. When he learns of an unsolved murder committed at a mental institution, Barrett devises a scheme to solve it and earn himself recognition. With the assistance of a psychiatrist and his girlfriend, Barrett convinces the doctors at the institution to commit him. Once inside, he begins his investigation -- and gradually loses his mind.