Cymbeline is bidding farewell to Lucius. Lucius says he is sorry that he has to report to his master that Cymbeline is his enemy. Cymbeline explains that the Britons will not endure Caesar's domination, and for the King to show less desire for independence than his subjects would appear "unkinglike" (line 7). Cymbeline gives Lucius safe conduct to Milford Haven.
Cymbeline says that he must prepare the army to fight the Roman forces, which are in Gallia (France) and ready to invade.
Cymbeline asks the Queen where Imogen is: she has lately had more of a look of malice than of duty towards him. The Queen urges him to treat her gently, and says time will heal. An attendant reveals that the doors to her rooms are locked and their knocks have gone unanswered. The Queen tries to reassure him by explaining that Imogen has asked her to excuse her staying in; she has not been feeling well. The Queen says she forgot to tell him this.
The King is alarmed, and leaves. Cloten remarks that he has not seen Pisanio either for two days. He follows the King. The Queen, left alone, prays that Pisanio's absence is explained by the fact that he has swallowed her poison. She wonders if Imogen has either killed herself or run after Posthumus; either outcome would suit the Queen, since then her son Cloten would be heir to the throne.
Cloten re-enters and confirms that Imogen has fled. The King is in a rage. The Queen is secretly pleased, as she hopes that Cymbeline's wrath will prove fatal to him. She exits. Cloten speaks about his feelings for Imogen, saying he loves her for her unrivalled qualities, but hates her for disdaining him and favoring Posthumus. He wants revenge on her.
Pisanio enters and Cloten aggressively interrogates him as to Imogen's whereabouts. He asks if she is with Posthumus. Pisanio feigns ignorance, saying Posthumus is in Rome so she cannot be with him. Cloten threatens to kill him unless he tells all. Pisanio presents him with a letter (later revealed to be a forgery, in Act 5, scene 5, line 279), seemingly from Posthumus, saying that this is all he knows of her flight. Pisanio is confident that the letter will not put Imogen in danger as she is far away, and hopes it may disconcert Cloten, as it is an apparently loving letter.
Aside to the audience, Pisanio says he will write to Posthumus saying that Imogen is dead. He prays for her safe return.
Having read the letter, Cloten offers Pisanio preferment if he will serve him, and do whatever "villainy" Cloten asks of him (line 113). Cloten observes that since Pisanio has loyally served the "beggar" Posthumus (line 121), he will surely be loyal to him also. Pisanio agrees.
Cloten asks Pisanio if he has any of Posthumus's clothes, and Pisanio says he has the suit Posthumus wore when he took leave of Imogen. Cloten asks him to fetch the suit. When Pisanio has left, Cloten reveals that he intends to travel to Milford Haven. Because Imogen once said he revered Posthumus's garment more than Cloten, he will put on the suit and "ravish her" (line 142), and kill Posthumus in front of her. That way, Imogen will see his "valour" to pay her back for her contempt. He wants both to sate his lust (line 146) and to get revenge on her.
Pisanio apparently overhears some of Cloten's speech, though we are not yet told this. He returns with Posthumus's clothes. Cloten asks him to take them to his room. He then asks Pisanio to be true to him. Pisanio replies that to be true to him would mean being false to that "true" man, Posthumus.
The imagery of buying and selling continues, with Cloten saying Imogen "outsells" all other women (line 75) and that Posthumus's base "weights" (line 89)-pieces of cheap metal-are worthless. But Cloten reveals once more his bestial nature, threatening to rip Pisanio's heart out (lines 87-8), a wolf-like and predatory image.
There is irony in Cloten's ordering Pisanio to perform "villainy" in his service, which he says will prove him "honest" (lines 113-5). This is indicative of the perverted values of the corrupt court that Belarius warned his adopted sons about: the good man is punished, the bad rewarded. Pisanio expands this theme in lines 162-7, where he says that to be true to Cloten would mean being false to Posthumus, whom Pisanio believes is "true," that is, good. This interpretation has been questioned by critics who view Posthumus, after his fall into jealousy, as being far from true. However, it is clear that Pisanio believes Posthumus to be an essentially true man who was abused by a villain.
In a chilling twist on the outward appearance versus inward reality theme, Cloten will wear Posthumus's garment in an attempt to wreak revenge on Imogen for saying that she valued it above him. He is also attempting to steal some of Posthumus's perceived worth by adopting his garment-a typically superficial act on his part.
There is a parallel plot theme in Cloten's plan to clothe himself in Posthumus's suit while in the next scene, Imogen appears dressed as a boy. This throws into relief the difference in their motivations: Cloten wishes revenge on Imogen, who he feels has wronged him, whereas Imogen feels only love for Posthumus, who has certainly wronged her. This leads us into one of the grand themes of the Romance plays, forgiveness and reconciliation. A character's redemption or otherwise largely depends upon their ability to forgive and be forgiven.
Cymbeline: Novel Summary: Act 3 Scene 5