Based on Shakesphere's play, Verdi's opera depicts the devastating effects of jealousy, "...the green-eyed monster which doth mock the meat it feeds upon". Believing Otello has promoted the fast-rising Cassio over himself, Iago plots to destroy both Cassio and Otello. Iago convinces the jealous Otello that his beautiful wife Desdemona is unfaithful, and that Cassio is her lover. Jealousy is followed by tragedy, then retribution, "Has Heaven no more thunderbolts?"