The Mexican pairs Brad Pitt with Julia Roberts in a dream casting coup that promises a road movie of blissful comic romance and delivers a series of dramatic dead ends. Pitt plays Jerry, a low-rent mob bagman whose girlfriend, Samantha (Roberts), dumps him when he takes on a new assignment instead of going straight as he promised. As Jerry crosses the border to collect an antique gun, called the Mexican, Samantha heads to Vegas to forget him. That is, until she’s taken hostage by mob hitman Leroy, played by James Gandolfini — Mr. Tony Soprano himself — in the film’s best performance. In case you’re not getting the drift, Pitt and Roberts don’t have many scenes together, since J.H. Wyman’s script is filled with distracting side trips, including flashbacks showing why the gun is cursed. Gore Verbinski, a director of commercials who debuted in features with 1997’s oddball Mouse Hunt, takes the odd route again by separating his star attractions for most of the film. As dumb ideas go, that one is a Hall of Famer.