After the high-flying adventures of the first Iron Man picture, the billionaire arms manufacturer and irrepressible bon vivant Tony Stark (Robert Downey Jr.) finds himself nursing a hangover. But not like any hangover he's had before: this one is toxic, a potentially deadly condition resulting from heavy metals (or something) bleeding out of the hardware he's installed in the middle of his chest. This is the problem Stark needs to solve in Iron Man 2, not to mention the threat from resentful Russian science whiz Ivan Vanko (Mickey Rourke), whose father helped create the Iron Man technology. There's an even bigger problem for the film: the need to set up a future Marvel Comics movie universe in which a variety of veteran characters will join forces, a requirement that slows down whatever through-line the movie can generate (although fanboys will have a good time digging the clues laid out here). Actually, the main plot is no great shakes: another Iron Man suit is deployed (Don Cheadle, replacing Terrence Howard from the first film, gets to climb inside), Stark continues to bicker with assistant Pepper Potts (Gwyneth Paltrow), and a weaselly business rival (Sam Rockwell) tries to out-do the Iron Man suit with an army of Vanko-designed drones. Mickey Rourke is a letdown, burdened by a wobbly Russian accent and looking skeptical about the genre foolishness around him, and Scarlett Johansson has to wait until the final couple of reels to unleash some butt-kickin' skills as the future Black Widow. That climax is sufficiently lively, and the initial half-hour, including Stark's smirky appearance before a Senate committee and a wacky showdown at the Monaco Grand Prix, provides a strong, swift opening. But the lull between these high points is crying for more action and more Downey improv. --Robert Horton