I wasn't prepared to like this movie as much as I did, but it turns out to be an intelligent character-driven suspense thriller.
George Clooney is in the title role. Michael works for a prestigious New York law firm, technically as a lawyer, but actually in a role variously described as a "bagman", "janitor", or "fixer." He's called upon to deal with Arthur (Tom Wilkinson), who's gone off his manic-depressive meds while doing a deposition in Wisconsin, removed his clothes, and pursued the deponent, a young Midwestern farmgirl named Anna, out in the parking lot. (Fortunately, we only see the beginning of this.)
But it turns out that Arthur is not only crazy, but right. The corporate client his firm is representing has been marketing a deadly herbicide that they know has a proclivity to kill people; if this gets out, they're likely to be on the hook for billions, and probably up against criminal charges as well.
George Clooney is dead solid perfect in this role, simply because he's so credible as an aging prettyboy whose charmed life is slipping into disaster on every side. He's got financial problems caused by entering into a bar business with his druggie brother; his ex-wife resents him for neglecting their young son, and so does the son; it's not clear what his long-term professional future is, since his firm is in merger talks, and it's not clear if they'll have any role for an ethically-challenged whose talents are in decline.
Unfortunately, all this wonderfulness is chained to the most hackneyed of plot devices, the corporation that retains murderous thugs to remove inconvenient trouble-making people who Know Too Much. I overdosed on this cliché when I saw it on Kojak for the eleventh time, sometime circa 1974. (The writer/director, Tony Gilroy, also wrote the Bourne films, which mine a slightly different lefty paranoia vein.)
But, given the politics of Hollywood, we're likely stuck with this sort of thing for the foreseeable future. If you suspend disbelief on that score, you'll see a pretty good movie.