On August 19th, 1561, Mary Stewart returned to Scotland; in May 1568, she left her kingdom for ever. During those seven years, what she did, what she was accused of doing, what she was expected to do, what she intended to do, formed the subject of the keenest interest and anxiety in England at the time; and the problems and mysteries of those years, never unravelled to this day, never with any certainty to be unravelled at all, continued to perplex English statesmen and to complicate the situation in England for nearly nineteen years more. We shall have to follow them therefore in much greater detail than would _a priori_ seem justifiable in a volume ostensibly dealing not with Scottish but with English History. During these same years it may be said that the great antagonisms were formulated, which were to rend the two great Continental monarchies for forty years to come. Thus in order to follow the subsequent story efficiently even from the purely English point of view, we must devote what may seem somewhat disproportionate attention to foreign affairs, which do not appear at first sight to have a very intimate connexion with events in England. For France these events may be summed up as the opening of the set struggle between Catholics and Huguenots; for Spain, as the preliminaries to the revolt of the Netherlands: while for all Europe, the effective sessions of the Council of Trent laid down finally the sharp dividing line between Protestant and Catholic--terms which have a well defined political meaning, in neither case identical with their original or correct theological import, in which latter sense half the Protestant world continued to assert its claim to membership in the Catholic Church. [Sidenote: (1) The Council of Trent]