The ensign bides his time. He sees his opportunity when the Moor degrades the captain for wounding a soldier and Desdemona tries to make peace between her husband and the captain. The ensign hints that Desdemona has her own reason to want the captain reinstated. When his wife claims that the demotion was an overreaction, the Moor becomes very angry and suspects that his ensign had spoken truthfully. When the ensign tells the Moor that the captain told him of the affair, the Moor demands to see proof of it.
The ensign and his wife have a daughter aged about three, and one day when Desdemona visits their house, he puts the child on her lap. As Desdemona and the child play, the ensign steals one of her handkerchiefs. The ensign then leaves the handkerchief on the bed of the young captain, who recognizes it and goes to return it to Desdemona. When the Moor answers his knock at the door, the captain runs away, but not before the Moor recognizes him.
Later, the ensign laughs and jokes with the captain where the Moor can see them; he then tells the Moor him that he and the captain were talking about the captain's love affair with Desdemona and a handkerchief that she had given him. The Moor, believing that the handkerchief constitutes proof of his wife's infidelity, demands it of his wife, who, of course, cannot produce it. The Moor decides that he must kill his wife and plots with the ensign to kill both his wife and the captain.
