Modern fiction has a certain way of achieving „literariness‟ and „sophistication‟; it does so by means of “ambiguity”. Being “witty” or “deceitful”, to quote William Empson, ambiguity seems to press home the writers‟ intention of deferring the meaning by making the ontological status of the text as implicit as possible. Ambiguity, therefore, forms a kind of narrative that determines the writer‟s style. In James Joyce, however, particularly in the stories of Dubliners, this ambiguity is meant to reach a „mysterious‟ level. Joyce‟s “mysteries” are utterly different from commonly-believed, so-called textual “problems”. The problems can be solved, but mysteries should be “witnessed” and “attested” to be unfolded. Joyce‟s mysterious ambiguities bear his unique signature: they represent the complexity, significance, and survival of a “gnomonic” patterning. Being a geometric figure, a gnomon is the part of a parallelogram which remains after a similar parallelogram has been taken away from one of its corners. The gnomon, therefore, represents an incomplete figure, like Joyce‟s vaguely elliptical and incomplete stories. Joyce introduces the gnomon as the personification of imperfection, hopeless, paralysis, and damnation. The following study is going to elaborate this main principle of Joycean ambiguity in the opening story of Dubliners, “The Sisters”, and demonstrate its distinctively gnomonic narrative and characterization.