Final answer:
The new theme introduced in Gawain's story is the conflict between appearance and reality, as Gawain appears brave but is actually fearful and tempted. This theme is highlighted by the contrast between his actions and internal struggles.
Step-by-step explanation:
The new theme introduced in Gawain's story is the conflict between appearance and reality. While Gawain appears to be brave and honorable, he is actually fearful and tempted by his own desires. This theme is highlighted by the contrast between Gawain's outward actions and his internal struggles.