Outside the army's camp, the First Lord and Second Lord Dumaine wait with a party of their men to capture the unfortunate Parolles. They decide to disguise their voices by speaking nonsense, and pick a soldier whose voice is unfamiliar to their victim to act as "interpreter." Parolles comes along soon enough, debating with himself how to make it look like he attempted the recovery of the drum without exposing himself to any danger. He considers giving himself a flesh wound, or ripping his clothes, and then wishes aloud that he had one of the enemy's drums, so he could pretend to have taken it. Then, screaming nonsense words, the group of soldiers falls upon him, binds him and blindfolds him. The ruse works--he believes himself to be captured by the enemy.
In the Widow's house, Bertram pleads with Diana to agree to sleep with him, professing his love for her. After much prodding, she agrees to allow him to come to her bedroom late that night, but she demands the ring of his finger as a token of his love. He reluctantly gives it, telling her that the ring is the emblem of his family; in return, she makes him wear a ring of hers. In fact, the ring Diana gives him comes from Helena--it was a gift given to her by the King of France after his recovery. Bertram departs, convinced that he has won a pleasure-filled evening for himself.
Back at the camp, the two Lords Dumaine discuss Bertram's conduct. His mother's letter, condemning his behavior, has arrived, and so has the false news that Helena has died in a monastery--a rumor spread, no doubt, by Helena herself. When Bertram returns from visiting Diana's bedroom, where he has been successfully duped into sleeping with Helena, the Lords take him to the location where Parolles lies pinioned, and tell him to watch. Then the soldier picked as "interpreter" threatens Parolles with torture unless he tells all the secrets of his army. Parolles, terrified, complies, and then goes on to give extremely unflattering descriptions of Bertram and both of the Lords Dumaine. His bags are searched, and a letter is found addressed to Diana, urging her to sleep with Bertram in return for payment. Finally, they declare that they will kill him anyway, and Parolles, completely undone, weeps and begs for his life. Amid much laughter, the blindfold is removed, and Parolles is left a ruined, friendless man. Nevertheless, he is not entirely discouraged--he has lost his position at Bertram's side, but he accepts the reversal and decides to get on with his life.
The action is these scenes is taken up with unfolding the plots devised earlier--the Dumaines' exposure of Parolles, and Helena's entrapment of her husband. The latter would seem to offer the greatest opportunity for laughs, but Elizabethan decorum requires that the sex take place off-stage: we must infer the success of Helena's ruse, since when Bertram returns to camp, he behaves as though his seduction of Diana was a triumph. What we see, in scene ii, is Diana seducing Bertram, as her honeyed words convince him to give up his ring. Her success proves her to be every bit as able a manipulator as Helena, and reconfirms the impression of Bertram as a fool everywhere but on the battlefield.
The unmasking of Parolles, meanwhile, is played for deliberate comic effect, especially in the ludicrous nonsense language that his captors speak--ostensibly in order to disguise their voices, but mainly, one imagines, because Shakespeare took pleasure in having his characters speak lines like "Throca movousus, cargo, cargo, cargo. / Cargo, cargo, cargo, villianda par corbo, cargo." Surrounded by voices intoning these ridiculous syllables, Parolles' fear is so strong that he almost becomes likable--he has no illusions about himself, certainly, and willingly abandons any pretense to honor when his life is threatened. The very eagerness with which Parolles falls over himself to denounce his former friends to the "enemy" is so baldly self-serving that the audience may agree with the First Lord's comment, made while Parolles is describing him as dishonest and corrupt--"I begin to love him for this"(IV.iii.286). Parolles may be a rogue, but after enduring four acts of the supposedly "noble" Bertram, a little roguery can be appealing. Indeed, Bertram's priggish disillusionment with his former friend hardly excites the audience's sympathies, since Bertram has no one but himself to blame. Everyone else saw through Parolles from the beginning.
A true villain, once revealed, must repent or die. But Parolles is strictly a minor rogue, able to easily roll with life's punches. "If my heart were great," he remarks at the end, alone and friendless, "'Twould burst at this" (IV.iii.345). If his heart were great--but it isn't, he is no tragic hero or impassioned villain, but only a harmless fraud. "Captain I'll be no more," Parolles says with a little wistfulness, "But I will eat and drink and sleep as soft / As captain shall . . . There's place and means for every man alive. / I'll after them" (IV.iii.346-55). In a sense, his pragmatism makes him Helena's spiritual brother, at least in ruthless practicality. Neither of them waste time on the inner turmoil characteristic of other Shakespearean characters: Helena loses her love and sets about getting him back my the most pragmatic means available; Parolles loses everything, but instead of bemoaning his fate, he shrugs and moves on, looking for greener pastures.