Walter Lesly invites the girl to drink. He then makes off with her; he intends to marry her (for her money). But he falls asleep before she does, and she escapes. She outruns his men and makes her way home.
There was a Walter Leslie who married the heiress of the Earldom of Ross in the reign of David II of Scotland; he was involved in many political quarrels in the reign of the next king, Robert II, and died in 1382. Another Walter Lesley was a crusader in this period. There is no reason to connect either with the villain of this piece except similarity of names (and, of course, the fact that there was a lot of this sort of thing in the anarchic Scotland of Robert II). - RBW