In Wales, near Belarius's cave, Imogen enters disguised as a boy. She is lost, has slept rough for two nights, and is on the point of collapse from lack of food. She reflects that to lie when prosperous is a greater crime than to lie out of need, and so falsehood is "worse in kings than beggars" (line 14). On this basis, Posthumus is among the false ones.
She notices Belarius's cave. She fears to make herself known, but starvation gives her courage. She calls out, but receives no answer, so draws her sword and enters the cave.
Imogen's clear-sightedness is evident in this scene. She does not try to attenuate Posthumus's guilt but recognizes that he is false even as she states her love for him.
The chance that Imogen should come across the cave where her lost brothers live can strike modern audiences as coincidental to the point of absurdity. But such remarkable happenings, particularly involving lost royal children, are part of the Romance tradition.
Some modern critics have embraced the magic elements of Romance and placed them within the framework of Jungian psychology, which sees events and characters as different aspects of the Self. In this framework, the aim is to bring to conscious awareness all the 'lost' aspects of the Self, resulting in unity of life and purpose. Thus, the lost royal children can be seen as representing the youthfulness and energy that the court has lost. They can also represent parts of Imogen's scattered self. She has been rejected or abused by the major male figures in her life, and to be embraced by her brothers must come as a healing experience.
Cymbeline: Novel Summary: Act 3 Scene 6