The Return of Eliot Ness (1991)

In 1947 when a cop whom Eliot Ness worked with when he was in Chicago is killed, he goes back to Chicago for the funeral. When he arrives, there's a lot of talk that his friend was dirty which Ness doesn't believe. He learns the man's own son also a cop thinks it's true. Ness was about to leave when he decides to stay and try and prove his friend is not dirty. He starts by teaming up with the man's son and investigating the case his friend was working on when he was killed, which involves one of Capone's associates.