Iago, Dez & Emilia get to Cypress; Othello's boat follows. Iago spies Dez & Casio saying "hello" and devises a plan... Dez's devotion to her husband is as clear as Iago's hatred for Othello.
The Herald tells the audience that the Turks were all killed/drown in a storm. The war is over. There was no need for battle & now they party.
Cassio gets drunk and fights Montano (Iago's plan); he then loses his rank as officer, again a part of Iago's plan- cassio is devastated. Iago's phase 2 plan is for Cassio to talk to Dez(he will then get Othello jealous of the 2 of them- remember the "hand kiss"?). Rodrigo runs out of money& Iago runs out of time or energy for him- he will make Emilia attend to Dez from here on out.