It's tempting to just think of Christopher Plummer as Capt. von Trapp and little else, but a casual glance at his stage credentials illustrate that he was well chosen for his title role in this Shakespearian tragedy. This adaptation also benefits from being a British/Danish co-production so was even filmed in Elsinore, too. You'' probably know the stroy of the eponymous Prince who has lost his father and seen his mother "Gertrude" (June Tobin) remarried to the new king "Claudius" (Robert Shaw). Now he, and his best pal "Horatio" (a passable Michael Caine) must tread a very fine line as they…