Iago is angry that Othello (the general of the army), has promoted Cassio to be his lieutenant instead of him. Othello secretly marries Desdemona, the daughter of a senator in Venice (Brabantio). Iago therefore tells Desdemona’s father about the secret marriage to cause trouble for Othello.

Desdemona’s father makes a formal complaint about Othello’s behaviour to the Duke of Venice. His complaint is ignored and the Duke sends Othello to Cyprus to continue fighting in a war. Othello goes to Cyprus and takes his new wife Desdemona with him, together with Iago and Michael Cassio.

Iago encourages Cassio to get drunk whilst on duty. Cassio ends up in a drunken fight and is demoted from his position as lieutenant. Iago begins to plant seeds of suspicion in Othello’s mind about his wife’s relationship with Michael Cassio. Iago gets hold of a handkerchief belonging to Desdemona and hides it in Cassio’s room pretending it is proof of Desdemona’s unfaithfulness.

Desdemona pleads with Othello to give Cassio his job back. She does this innocently, but Othello takes this as proof of her feelings for Cassio. Iago continues to manipulate Othello to the point where Othello murders his new wife as punishment for her supposed unfaithfulness. Iago’s wife, Emilia, tells Othello that Iago has lied. Othello realises his tragic mistake and commits suicide over the body of his wife as Iago is arrested.