"This is a subtle whore, A closet lock and key of villainous secrets; And yet she'll kneel and pray. I have seen her do't."
"Heaven truly knows that thou art false as hell"
Othello quizzes Emilia about Desdemona's infedility, Emilia in response would do such a thing and that she is innocent, Othello asks her to get Desdemona for him
"What, not a whore"
With Emilia gone, Othello goes on to call her a brothel-keeper "bawd" and suggests that Desdemona is keeping dark secrets and he cannot believe that she is acting so virtuous when she is comitting adultery.
"nor answers, have I none"
Desdemona arrives and Othello dismisses Emilia. He then goes on to accuse Desdemona of keeping secrets from him, Desdemona is unaware of what he is talking about and suggests that he could be upset because of him being called back to venice.
"Some eternal villain...Have not devised this slander"
Othello carries on, suggesting that Desdemona is "false" and calls her a whore to her face and again, Desdemona states that she is innocent and unaware of what he is talking about.
Othello exits but not before telling Emilia to keep what she may have heard to herself. Emilia asks Desdemona what is going on with Othello but Desdemona doesn't have anything to tell her
Iago arrives and also asks what is going on, but Desdemona is too distressed to tell the tale. Emilia informs him that Othello called Desdemona a "whore" and suggests that a villain has plagued Othello's mind.