Cloten, now in Wales, reviews his superiority to Posthumus and repeats his vile plan, also thinking it will go over all right back at the British court thanks to his mother's influence.
"If Iachimo is his summing up of all that is ungentle in the continental gentleman, so is Cloten of all that is ignoble in the English nobility" (Goddard, II 251). "Iachimo plainly stands for Italy and her malign influence, Cloten for corrupt English nobility, and Belarius-Guiderius-Arviragus for the ancient English tradition handed on, uncontaminated, to England's youngest and most genuinely noble blood" (Goddard, II 256). Iachimo's lust for Imogen has been transferred to Cloten, like the Iago and Roderigo situation in Othello (Farina 94).
While the men go hunting, Fidele is to remain at home. Still heartsick, she decides to try some of that medicine, and she returns to the cave. Cloten stumbles along, and Belarius recognizes him, worrying that he's come to arrest them. While Belarius and Arviragus go off to see if Cloten has other cohorts with him, Guiderius emerges before Cloten. He and Cloten exchange insults, the latter, as always, arrogant and insufferable. So they fight.
Belarius and Arviragus return, the former certifying that he recognizes Cloten from years ago. Guiderius enters carrying Cloten's severed head: "Not Hercules / Could have knock'd out his brains, for he had none" (IV.ii.114-115). "His death is like the death of a beast or monster" (Garber 810). Guiderius had used Cloten's own sword. Belarius worries about the consequences of this slaying. Indeed, so should Shakespeare: "having the head of a queen's son thrown to the fishes otherwise might have bothered the theatrical censor" (Bloom 629). They return to the cave and find Fidele, apparently dead. They grieve and the brothers sing a dirge (IV.ii.258ff): "Beautiful as this is, it is one of the darkest elegies, centering on 'fear no more' as the only consolation for dying" (Bloom 630). "'Golden lad' and 'chimney-sweeper' were folk names for the dandelion, so this resonant passage, which seems to comment on early promise and loss and the hardships of the working world, is also an embedded nature fable with the implication of rebirth (the 'dust' of the dandelion is the seed head that scatters)" (Garber 814). "The flowers are the flowers of romance and fantasy, the blood is the blood of tragedy and history" (Garber 826).
Belarius brings back Cloten's headless corpse, which is dressed like Posthumus, and lays it next to Imogen for burial later. Imogen wakes up but still wonders if she's in a dream; "as so often in this play it is difficult to strike the right balance -- or to know whether there is a right balance -- between reactions of horror and laughter" (Wells 356). "The gouging out of Gloucester's eyes may be more cruel, but it is less nauseating" (Wells 255). She eventually comes to think it is Posthumus' body next to her, killed by Cloten and Pisanio. She faints on the body. "The ideal purity of womanhood embracing -- because it is clad in the garments of the loved one -- the brutal villainy of a false nobility that sought to enforce it: here is a situation that may mean more than meets the eye at first glance" (Goddard, II 256).
Caius Lucius and the captains of the Roman army, geared for battle, listen to a soothsayer mention an eagle disappearing into the sun. They take this as a sign of their coming victory. They discover Imogen/Fidele on the corpse and wake her. She says this was her master, killed by mountain-men, and is taken into Lucius' service. "Grieved, she is carried off, kindly enough, by the Roman general Lucius, and will not speak again until the long reconciliation scene that concludes the play" (Bloom 629).
The Queen is ill, supposedly over the disappearance of Cloten, and Cymbeline is depressed over Imogen's absence. Pisanio claims not to know where she is. The Romans, it is reported, have invaded the coast, so the King and others leave for the war while Pisanio puzzles over why he hasn't heard from Posthumus.
The heavens still must work.
Wherein I am false, I am honest; not true, to be true.
These present wars shall find I love my country,
Even to the note o' th' King, or I'll fall in them.
All other doubts, by time let them be clear'd,
Fortune brings in some boats that are not steer'd.
Belarius is hesitant to side with Britain in the war because of Cloten's slaying. If they try to enlist, their address would raise suspicions and they'd eventually be found out. But the boys convince him he's worrying too much: the army has too much to do to bother with a Cloten investigation. They all patriotically rally and go off to join up.