The revised series of The Untouchables with Tom Amandes as Eliot Ness did a much better episode of the famous Jake Lingle killing. In that one the real figures of Al Capone and Bugs Moran and their various supporters were all involved and the unsolved killing got a more plausible explanation.
Herb Vigran plays the reporter who was a crusader to the public who read his columns, but after his assassination was quickly discovered to have been a go between shuttling for news and payoffs from any mobster who had it to pay. After his death Lingle's public image eroded rapidly and in real life Robert Stacks's crew of Feds were peripherally involved at best.
The main character here is Jack Lord who is a puzzle to me after I've watched the episode. He's a self styled cynical hood who offers to go inside one of the mobs to get information on the killing for a price. The mob he goes inside of is Charles McGraw's.
After seeing the film the story made absolutely no sense either in character or motivation. A really nice cast with some of the best players around is really wasted here.