Jon Cleary's novel is the basic source from which director Fred Zinnemann's inspiration springs. Between Cleary and Zinnemann lies Isobel Lennart's perceptive, virile screenplay, loaded with bright, telling lines of dialog and gentle philosophical comment. But, fine as the scenario is, it is Zinnemann's poetic glances into the souls of his characters, little hints of deep longings, hidden despairs, indomitable spirit that make the picture the achievement it is.