The poem never reveals the motive of Lord Randall's lover in giving him the poisoned "eels fried in broo." He gives evidence to his mother that suggests his "hunting hounds" may have also ingested the nasty eel concoction, because they "swelled and they died," foreshadowing that the lord may face a similar fate.
There are several different versions of the "Lord Randall" poem. One of the versions has four additional stanzas in which Lord Randall lists his bequeathments, what he wishes to leave to his family members. In this version, Lord Randall comments that he would leave his lover "hell and fire," thus reflecting his bitterness at her betrayal of him. Perhaps the lover poisoned him in hopes to gain his estate, but Randall smartly leaves "his house and lands" to his brother; to his sister, he leaves his "gold and silver." The fact that his last thought are to his estate and monetary wealth could be interpreted as his desire to protect his holdings from the murderous grasp of his lover, who in the end, he has nothing for her but "hell and fire."