The darkest cloud upon his memory is his alleged conduct in reference to Argyle's trial. The charge against him is that, when the evidence proved inconclusive, Monk produced some private correspondence upon which the marquis was immediately convicted. The story has hitherto rested on the testimony of Burnet, a notorious libeller of the general's, and Baillie, who, like the rest of the Presbyterians, could never forgive him for foiling their attempt to force upon the country a covenanted King. No evidence could be more tainted, and it is not surprising that the story has always been doubted, seeing how inconsistent it is with the character of a man "who could not hate an enemy beyond the necessity of war." Injudicious advocates have even denied the fact altogether, but a bundle of Argyle's letters, including some to Monk and one to his secretary, was certainly produced at the last moment, and at once sealed the prisoner's fate. In consequence of Charles's resolution not to go behind the Scotch amnesty of 1651, the chief point in Argyle's indictment was that he had adhered to the King's enemies, or, in other words, that he had opposed the last Highland insurrection. The leaders of it were at once his judges and his prosecutors, and they were determined to have their revenge. The case closed and still there was no real evidence, when just as the Court was deliberating its judgment a messenger thundered at the door with the fatal packet from London. Regardless of all law the case was reopened, the letters read, and Argyle condemned. The question of Monk's share in the infamous proceeding rests on the contents of those letters. They have now been found, and they acquit him for ever. Only two are to him, and they contain no evidence whatever beyond what had been already obtained in abundance. They are confined to little more than civilities. The one to Clarke, Monk's secretary, encloses a letter from Glencairn, and expresses Argyle's intention of keeping his own country neutral. The other three are to Lilburne, and they prove in the clearest manner that Argyle was not only giving the English general information of the Royalist movements, but was doing his best to prevent assistance going to the insurgents.[12] These three letters are not endorsed as having been "admitted" by the prisoner, and could any doubt remain that it was these on which he was convicted, it would be removed by the subsequent petition of Archibald the tenth Earl. For in that document he recites that the fatal letters bore no "signature" that the marquis "had owned them." The letters to Monk and Clarke are all endorsed with Argyle's admission.[13]