Warning: My manga "reviews" often contain spoilers. I find it hard to adequately discuss a volume of manga without talking about it in more detail than some might like.
Emma and William are still separated in most of this volume. William continues his transformation into the ideal aristocrat - becoming more and more miserable while doing so. The culmination of his new persona comes with the acquisition of Eleanor. The daughter of a viscount, Eleanor has been head over heels for William since the first volume. William finally decides to accept the chase. Eleanor is a nice enough girl, but just haven't the depth that Emma does. William cares for Eleanor halfheartedly; Emma is still at the forefront of his mind.
In the meantime, Emma is on her way to London with her mistress as a traveling companion. London brings back painful memories of William and Mrs. Stownar. It turns out that Emma's mistress and William's mother are friends, or at least acquaintances. Emma is "loaned" out to William's mother to be her companion for a party. Emma is dressed not as a maid, but as a beautiful lady-in-waiting. Now that Emma looks like a society girl, she's ready for the party. And who would she happen to meet at this party...
I continue to love the artwork in Emma. I like how Mori conveys emotion. When showing heightened emotions - sadness, embarrassment, etc - Mori draws entire spreads without using any words. We just see boxes showing the character's faces slowly reveal their feelings. It has a much greater effect on me than any words. The ending of volume 4 illustrates Mori's talent particularly well. One thing I didn't like was that there was nudity in this volume. Nothing much, really - just showing Emma's mistress naked as Emma helps her dress. But it wasn't something I have any interest in seeing and didn't further the volume in any way.