The other prisoner, Walter Stewart, proved a more valuable prize. To clear Argyll was after all no great matter, for Argyll was strong enough to clear himself. The important point was to convict Montrose. A letter to him from the King was discovered in the lining of Stewart's saddle. There was nothing in its language capable of being turned to his discredit, but it could be construed as an answer to some previous communication, and it certainly established the fact of a secret correspondence between the two which was contrary to the articles of the Covenant. And this was not all. Papers of a more suspicious nature were discovered--papers in Stewart's own hand, written in a strange jargon, where letters, phrases, and sometimes the names of animals were substituted for the names of persons. Stewart explained these as the heads of certain instructions entrusted to him by the Plotters to be delivered to the King through the hands of Lennox and Traquair. The _Elephant_ or _Serpent_ stood for Hamilton, the _Dromedary_ for Argyll, Montrose himself was the _Genero_, the letters _A B C_ signified the four conspirators--and so forth. The papers also contained some suggestions as to the preferment of Montrose and himself, and a warning that if they were neglected it would go ill with the King. Stewart, like his namesake, did not keep to one story. He altered much, added something, contradicted himself many times. Traquair, who was then in London, flatly denied all knowledge of the papers, nor would he believe that Montrose or any man of sense, if minded to play such a dangerous game, would have taken into his confidence a timorous half-witted fool like Stewart. The King wrote in his own hand to Argyll one of his ambiguous letters, committing himself to nothing beyond a declaration that his journey to Scotland had not been prompted by Montrose or Traquair to their own ends, but was intended solely to settle all disputes on the terms of the new treaty, and that he had given no promises of office to any man. He avowed his letter to Montrose as one fit to be written by a king to a good subject. Finally, he requested Argyll to do him right in this matter, and not permit him to be unjustly suspected. The day before this letter reached Edinburgh the four Plotters were arrested and sent as prisoners to the Castle.