Mary escaped by night from Lochleven, and joined the insurgents. The Regent gave chase, and caught her army up at Langside, near Glasgow. The queen's friends were routed in the fight that followed, and she herself, riding hard out of the fray, fled for the English border. After a moment's hesitation, she resolved to throw herself on Elizabeth's mercy, rather than to face the almost certain death which awaited her at the hands of her son's adherents. There was no time to wait for any promise of safe conduct or shelter, and she arrived at Carlisle, unprotected by any engagement on the part of the Queen of England (May, 1568). [Sidenote: =Mary confined In England.--The Casket Letters.=] Elizabeth's most dangerous enemy had thus fallen into her hands, but the position was not much simplified by the fact. It had to be decided whether the royal refugee should be allowed to proceed to France, as she herself wished; or handed over to the Scots, as the Regent Murray demanded; or kept in custody in England, as Elizabeth's self-interest seemed to require. To let her go to France would be generous, but dangerous; once arrived there, she would conspire with her cousins, the powerful family of Guise, against the peace of England. To send her back to Scotland would have some savour of legality about it, but would be equivalent to pronouncing her death-sentence; and from this Elizabeth shrank. To keep her captive in England seemed harsh, and even treacherous; for what right had one sovereign princess to imprison another? The politic Elizabeth resolved to take a cautious middle course. She protested to the Queen of Scots that she was willing to restore her to her throne, if she found that the accusations which her subjects made against her were untrue. This was practically putting her guest upon her trial for the murder of Darnley; for when the Regent and the Scots lords were informed of the decision, they came forward to accuse their exiled mistress. They laid before Elizabeth's commission of inquiry the famous "Casket Letters," a series of documents which had passed between Mary and Bothwell. If genuine--and it seems almost certain that they were--they proved the guilt and infatuation of the Queen of Scots up to the hilt. Mary protested that they were forgeries, and her followers down to this day have believed her. But she refused to stand any trial; declared that she, a crowned queen and no subject of England, would never plead before English judges, and demanded leave to quit the realm. Satisfied with the effect on English and Scottish public opinion which the "Casket Letters" had produced, Elizabeth now took the decisive step of consigning Mary to close custody; thus practically treating her as a criminal, though no decision had been given against her (January, 1569). [Sidenote: =Romanist intrigues in Mary's favour.=]