Guiderius notes that he, his brother, and Belarius are in danger from the Romans. Belarius suggests they retreat higher into the mountains. He says that because of Cloten's killing, they cannot go for protection to the King. If they are caught, they will be tortured and killed. Arviragus thinks that the King will be too busy with the war to look into their origins, but Belarius points out that he is well known in the army, and besides, the King has not deserved their service or love.
But Guiderius and Arviragus believe that they should all go to fight in the wars. Guiderius says he and his brother are not known by anyone at court, and Belarius is forgotten and "o'ergrown" (line 33), possibly meaning bearded and unrecognizable, or simply grown out of their thoughts. Guiderius and Arviragus ask for Belarius's blessing to go to war. Belarius replies that since they value their young lives so slightly, there is no reason why he should set more value on his old one. He joins them as they go off to fight.
The courage of Guiderius and Arviragus, contrasted with Cymbeline's lack of kingly valor in the previous scene, leaves no doubt that it is time for a regime change. Shakespeare's plays uphold the divinely ordained nature of kingship; thus, those who kill, depose or usurp a rightful king must always pay a price. But running alongside this is the idea that kingship is part of the great cycle of nature, in which old, sick and decaying branches wither and die, to be replaced by young, vigorous growth. Cymbeline is the decayed king, while his lost sons, nurtured in the womb of the wild Welsh countryside, are now ripe to assume royal roles.
Cymbeline: Novel Summary: Act 4 Scene 4