O Enviado de Satanás (1949)

After straight-arrow district attorney Joseph Foster says in frustration that he would sell his soul to bring down a local mob boss, a smooth-talking stranger named Nick Beal shows up with enough evidence to seal a conviction. When that success leads Foster to run for governor, Beal's unearthly hold on him turns the previously honest man corrupt, much to the displeasure of his wife and his steadfast minister.