Hitchcock dubbed this exhilarating comedy-thriller “my final word on the chase film.” Cary Grant’s Roger O. Thornhill (“O for Nothing”) is your basic gray-flannel-suited adman, until he is mistaken by the police for an assassin and by an international spy ring for a double agent. The ensuing chase carries him across the American landscape, where an effort to expunge him like just one more rural insect makes him fighting mad, and every national monument presents a new challenge to his true identity, not to mention his life.