Meanwhile, Helena has gone to Florence, where she overhears a conversation between an old Widow, her daughter Diana, and their neighbor, Mariana. It seems that Bertram, who rides by with the Duke of Florence's army as they talk, has been making overtures to Diana, hoping to get her in his bed. Helena joins the discussion, in which the older woman advises Diana to maintain her chastity. The three Florentine women have heard that Bertram has a wife he detests, but are unaware that Helen is the woman. After the conversation, Helena is invited to stay with the Widow.
In the Duke's camp, the First Lord and Second Lord Dumaine advise Bertram not to put his faith in Parolles, because the man is a boastful coward with no military experience and no loyalty. To expose Parolles, they devise a plan: they will goad him into attempting to retrieve his regiment's drum, which was lost on the field of battle (a military disgrace); then, disguised as enemy soldiers, they will "capture" him, blindfold him, and interrogate him, thus demonstrating to Bertram how quickly his loyal friend will turn traitor if his life is threatened. Encountering Parolles, they suggest that the loss of the drum was unimportant, and that he should forget it. Being cocky and boastful, Bertram's companion immediately swears that he will recapture it, or at least make a valiant effort. When he is gone, the two lords laugh, and tell Bertram that Parolles will do no such thing, being a coward. Bertram is skeptical, but invites the Second Lord to accompany him and meet Diana, whom he still plans to bed.
Meanwhile, Helena has revealed her identity to the Widow, and uses a purse of gold to buy her help in a scheme that, Helena hopes, will fulfill her husband's conditions for their marriage. Diana will obtain the ring that Helena needs from Bertram, as a token of his love; then, she will invite him to her bedchamber. In the darkness, Helena and Diana will switch places, and the oblivious Bertram will have sex with his true wife rather than the virgin. The Widow agrees, and tells Helena to go and secure Diana's cooperation in the plot.
Diana's virginity, which she jealously protects, returns us to the earlier bantering discussion Helena and Parolles shared on the subject. In that conversation, Parolles had argued that a woman ought to lose her maidenhead as soon as possible--now, appropriately enough, he is assisting Bertram in convincing a chaste young woman to give it up without benefit of wedlock. As for Bertram himself, our estimation of him sinks still lower, although given how he has behaved so far, this seems almost a small offense. For the Count, it is clear, war comes first, and women are an unimportant matter; they are there to dally and fornicate with, but not to marry.
The fact that seducing Diana is hardly worse than his abandonment of Helena does not in any way excuse Bertram's behavior; in fact, his behavior is bad enough to make the "bed-trick" seem perfectly justified. (This switch, in which a wife substitutes herself for a lover in order to trick an adulterous husband, is common in folklore, and Shakespeare uses a similar device with Mariana, Isabella, and Angelo in "Measure for Measure.") There are dubious elements involved here, of course, including the bribery of the Widow and the lies that Diana is forced to tell. But, ultimately, as Helena points out, the trick brings about the sexual union of man and wife--a good and moral end, for all that her husband believes that he is committing adultery. The audience cannot help being impressed with Helena's resourcefulness (and her certainty that she will get pregnant after just one sexual encounter!), and glad to see the odious Bertram fooled. Still, the episode leaves a bad taste in the mouth, and contributes to the view of All's Well as a "dark" play. In other plays, lovers consummate their union joyfully; here, it is done by treachery, with the implication that all men (or at least Bertram) are such lustful creatures that they cannot tell one woman from another. The view of human nature offered here is, to say the least, unpleasant.
Meanwhile, even as Bertram takes part in what he believes to be an adulterous affair, Shakespeare begins his (half-hearted) rehabilitation of the "hero." In a sense, since Bertram must be united with Helen at the play's end, a scapegoat is needed for his crimes--and Parolles, who is certainly a sufficiently unpleasant character, becomes the scapegoat. His exposure as a traitorous coward by the First and Second Lords is a case of Bertram's good friends triumphing over his bad companion--and hopefully, a step on the road to making Bertram a better person.