A lady courted by three kings weds one who is then slain (by one of the rivals/a rebel). Her not-yet-born child will be spared if female. She bears a boy, switches him with a baby girl. When grown the boy is told his heritage and avenges his father.
Some texts of this ballad share a verse with Elizabeth Halket Wardlaw's "Hardeknute" (for which see Volume II of Percy's _Reliques_; at that time, the authorship of Wardlaw (1677-1727) had not been established). This caused Scott to wonder about the authenticity of the piece, but Child thought the informant might have taken the verse from the "tiresome and affected Hardyknute, so much esteemed in her day." - RBW