No Way Out
The premise of the film is that the government suspects a "mole" has penetrated the highest levels of the Pentagon, or at least this is an idea that is floated around when convenient.
Costner stars as a heroic naval officer who becomes an intelligence liaison to Defense Secretary Bryce (Hackman). In a series of plot coincidences, Costner's character falls in love with a pretty girl who conceals from him the fact that she's Bryce's mistress. When Bryce and the girl quarrel and scuffle, she falls off a balcony and dies.
Bryce gets his homosexual lover to cover up the manslaughter crime, and they plant the story that the "mole" was responsible. The irony is that Costner is the only mole, that he didn't kill the girl, and upon learning of Bryce's guilt he wants revenge on the man who killed his lover.