Gary Cooper proves that there is a great deal more to his acting than spurs and saddles in this adaptation of George Du Maurier's fantasy drama. He portrays the eponymous character who after many years as a youth of dithering (Act 1), becomes an architect who lands a plum job refurbishing the stables on the estate of the wealthy "Duke of Towers" (John Holiday) (Act 2). After a fairly frosty start, he and the "Duchess" (Ann Harding) fall in love, a relationship of which the Duke is not entirely unaware. An altercation ensues, the "Duke" is killed and "Ibbetson" is jailed for the crime. What…