Jaina and Jacen return to Coruscant for a vacation and see an old friend, Zekk. But though the twins have had plenty of adventures, they've never experienced the problems Zekk has. Orphaned, destitute, without any support, Zekk has been making a living in the underworld of the city. He feels humiliated by his old friends' success and obvious privilege. They try to include him, but after he eats the centerpiece at a feast (thinking it to be a salad), he refuses to have anything to do with them. Instead, he is recruited by the Shadow Academy, where the witches twist and train him to be a dark Jedi.
It's fascinating to me that there are still serious class issues and poverty in the New Republic, but it makes sense--Lucas's universe is based on the ideal of elitism. For a young adult book, there is a great deal of tension here.