Wariston (accuses his wife of adultery and) strikes her. She avenges herself by killing him with the help of a servant. Lady Wariston is arrested and condemned. (She begs the King to lessen her sentence to beheading. He wishes she did not have to die.)
Child reports that this event is historical, but the judicial records of Lady Wariston's trial are lost. This ballad is therefore the only evidence of the motive for her murder of her husband.
This certainly appears to be a folk ballad, but it also appears to be extinct. Child knew three texts, all damaged, and the song has not been collected since. Ewan MacColl has a tune for it, but it's nearly certain that it came out of his own head. (Or, more correctly, is a modification of a tune for another ballad -- e.g. it's much like the tune I know for "The Dowie Dens o' Yarrow.")
Child treats this as one ballad, and given its lack of survival in tradition, there is no reason to break it up into two entries -- but I think it likely that it is in fact *two* ballads, one represented by Child's A and B texts and the third by his C text.
There are several reasons for this. The forms of the stanzas are different (though we might note that A and B also differ from each other). There are only a few common words, and most of them commonplace ("O Wariston, I wad that ye wad sink for sin").
Most crucial, though, is the complete difference in motive. In the A/B text, Wariston strikes his wife over a trivial quarrel. In C, however, Lady Wariston is a child bride (her age is given as fifteen at the time of her marriage; the real Lady Wariston seems to have been about nineteen). Shortly after their marriage, Wariston goes to sea; before he returns a year later, she bears a child.
Upon his return, Wariston accuses his lady of adultery and casts her out. The murder is her retaliation. - RBW