This generation’s scariest Frenchman has got to be Vincent “Mesrine/Black Swan” Cassel, who gets another workout on the other side of the law in Danny Boyle’s “Trance.” He’s got to be menacing, scary to James McAvoy, the art auction house employee he’s threatening, and sexy/scary to Rosario Dawson, the hypnotist the hoods round up to put our “hero: in a trance to figure out where some missing art’s gone. Cassel has a magnificent sneer and a psychotic glare, and is just catnip to the ladies. “Trance” opens in the US later this spring.