In November the Congregation, after a severe defeat, fled in grief from Edinburgh to Stirling, where Knox reanimated them, and they sent Lethington to England to crave assistance.  Lethington, who had been in the service of the Regent, is henceforth the central figure of every intrigue.  Witty, eloquent, subtle, he was indispensable, and he had one great ruling motive, to unite the crowns and peoples of England and Scotland.  Unfortunately he loved the crafty exercise of his dominion over men’s minds for its own sake, and when, in some inscrutable way, he entered the clumsy plot to murder Darnley, and knew that Mary could prove his guilt, his shiftings and changes puzzle historians.  In Scotland he was called Michael Wily, that is, Macchiavelli, and “the necessary evil.”

In his mission to England Lethington was successful.  By December 21 the English diplomatist, Sadleyr, informed Arran that a fleet was on its way to aid the Congregation, who were sacking Paisley Abbey, and issuing proclamations in the names of Francis and Mary.  The fleet arrived while the French were about to seize St Andrews (January 23, 1560), and the French plans were ruined.  The Regent, who was dying, found shelter in Edinburgh Castle, which stood neutral.  On February 27, 1560, at Berwick, the Congregation entered into a regular league with England, Elizabeth appearing as Protectress of Scotland, while the marriage of Mary and Francis endured.

Meanwhile, owing to the Huguenot disturbances in France (such as the Tumult of Amboise, directed against the lives of Mary’s uncles the Cardinal and Duc de Guise), Mary and Francis could not help the Regent, and Huntly, a Catholic, presently, as if in fear of the western clans, joined the Congregation.  Mary of Guise had found the great northern chief treacherous, and had disgraced him, and untrustworthy he continued to be.  On May 7 the garrison of Leith defeated with heavy loss an Anglo-Scottish attack on the walls; but on June 16 the Regent made a good end, in peace with all men.  She saw Chatelherault, James Stewart, and the Earl Marischal; she listened patiently to the preacher Willock; she bade farewell to all, and died, a notable woman, crushed by an impossible task.  The garrison of Leith, meanwhile, was starving on rats and horseflesh:  negotiations began, and ended in the Treaty of Edinburgh (July 6, 1560).

This Treaty, as between Mary, Queen of France and Scotland, on one hand, and England on the other, was never ratified by Mary Stuart:  she appears to have thought that one clause implied her abandonment of all her claims to the English succession, typified by her quartering of the Royal English arms on her own shield.  Thus there never was nor could be amity between her and her sister and her foe, Elizabeth, who was justly aggrieved by her assumption of the English arms, while Elizabeth quartered the arms of France.  Again, the ratification of the Treaty as regarded Mary’s rebels depended on their fulfilling certain clauses which, in fact, they instantly violated.