"Morning Star" is by the Anglo-Welsh actor Emlyn Williams, who was first introduced to New York as the author of the excellent theatrical thriller called "Night Must Fall" and who later revealed his more earnest side in "The Corn Is Green." It is the writer of the second, not the writer of the first, who is recognizable in the new play, but "Morning Star" is, nevertheless, not nearly so good as "The Corn Is Green." Probably the explanation is simple enough. In "The Corn Is Green" Mr. Williams was concerning himself with a group and a milieu which he knew more intimately than most people know them, and he had, accordingly, something of his own to say. In "Morning Star" he is concerned in a very general way with England's reaction to the war, about which he can neither say anything particularly original nor feel anything more poignant...