I can't add too much that hasn't already been said. A 1985 film, the plot should be familiar to anyone with or without basic cable by now. Where this film shines is in the relationships between the characters and the quality of the acting. Mind you, the plot and action aren't shabby, either, despite some comments here to the contrary.
Perhaps this is merely middle-age fantasy - how many middle aged dads (or moms) haven't had the fantasy of showing their sullen kids how cool they once were and could be again if necessary? I was fortunate not to have any sullen kids (or grandkids), but I've been in this guy's place and I recognized the looks on both faces. (OK, I was never a spy or anything so overtly cool, but I did have my moments.) The point is that there come inevitable times in the relationships between kids and parents when the kids suddenly realize that the old folks may have actually been cool before the kids even knew what cool was all about, and that's the heart of this film.
Contrary to some comments, the plot is quite coherent with only a few holes which I won't elaborate. Some of the carping about plot points I've read here must have come from people lacking in either imagination or comprehension. The action is credible both in its pacing and execution. Not Arthur Penn's best film, but this is as much of an actor's film as a director's film.
The acting is uniformly good, but Hackman holds the center of the film. If he weren't completely believable, the whole effort would fall apart. Matt Dillon gives a very good performance as Hackman's son/foil, but isn't in the same league. The usually reliable Josef Sommer gives a surprisingly weak performance - OK, but not up to his usual work. The late Herbert Berghof (husband of Uta Hagen and co-founder with her of the eponymously named HB acting studio) gives a master class in his portrayal of a truly sympathetic, tortured soul - not much screen time, but a real gem. Another standout is Viktoriya Fyodorova, who offers some of the films most poignant scenes as Hackman's love-who-might-have-been, who devotes herself to helping him and his son find his kidnapped wife.
Highly recommended, but it won't really resonate with the kids...