The movie is told from Eric O'Neill's perspective. O'Neill, portrayed by Ryan Phillippe, was assigned to befriend and work with Hanssen. Hanssen is portrayed by Chris Cooper who pretty much reprises the similar white, middle-aged, conservative, homophobic, manipulative character with secret sexual activities he played in 1999's American Beaty. Laura Linney's scenes as Agent Kate Burroughs were probably the most compelling and interesting moments of the movie.
My interest in the movie was sparked by the Fresh Air interview with Eric O'Neill and director/screenwriter Billy Ray. Unfortunately, the radio interview was more interesting than the movie. The scenes described by Eric O'Neill seemed to be more suspenseful as described in the radio interview than the movie.
I usually like movies that are careful to recreate actual events like the other movie Billy Ray directed, 2003's Shattered Glass. I'm not quite sure what is missing in this film. I suppose it is possible to make a movie too realistic.