As to his making his escape, that did not appear to be a very difficult undertaking now that he had a friend outside.

The watch kept up was not a very vigilant one, for such numbers of prisoners were taken on both sides that they were not regarded as of very great importance, and indeed the difficulty lay rather in making across the country to the Southern border than in escaping from prison; for with a friend outside, with a disguise in readiness, that matter was comparatively easy.

All that was required for the adventure was a long rope, a sharp file, and a dark night.
The chief difficulty that occurred to Vincent arose from the fact that there were some twenty other prisoners in the same ward.

He could hardly file through the bars of the window unnoticed by them, and they would naturally wish to share in his flight; but where one person might succeed in evading the vigilance of the guard, it was unlikely in the extreme that twenty would do so, and the alarm once given all would be recaptured.

He was spared the trouble of making up his mind as to his plans, for by the time he had finished his letter the hour that the hucksters were allowed to sell their goods was passed, and the gates were shut and all was quiet.
After some thought he came to the conclusion that the only plan would be to conceal himself somewhere in the prison just before the hour at which they were locked up in their wards.