Too bad the best part of the movie, Dreyfuss in a dry but affecting performance as a magician with a criminal streak, is killed off a third into the story. That leaves Slater, with all the emotional range of a sock puppet, to carry the show, not only as the narrator (nasal monotone), but as a hostage and mastermind forger who gets himself put back into prison to dig up the diamonds. Slater's not a leading man; his head is too big for his body and he's still channeling Jack Nicholson (as Critical…