Birdlime

At the end of Act I, Iago explains that he will tell Othello that Desdemona is having an affair with Cassio. Othello believes Iago to be a good man and so will believe what Iago tells him. Othello will be crushed by Desdemona’s apparent unfaithfulness, and Cassio will be discredited. With Cassio and Othello in the throes of scandal, Iago hopes to be nominated lieutenant, and Roderigo hopes to get with Desdemona.
After the first two scenes of Act II, Iago’s plan seems to be coming together. When Desdemona arrives in Cyprus, Cassio greets her by taking her hand and kissing his own fingers, considered a sign of politeness. These gestures of courtesy seem very innocent, but if looked upon in hindsight through a lens searching for infidelity, Cassio’s greeting will appear telling. Cassio also leans his head forward to whisper something to Desdemona, which could appear suspicious. Iago believes that Cassio has some amount of affection for Desdemona, which only makes Iago’s plan more possible. Iago is intelligent and quite manipulative, able to make people think he’s an honest person when the opposite is true, and his plan will likely work.