 Why is Thig's return to Earth bittersweet?
An hour later, his scars and altered cartilage already healed and painless, Thig again scraped sand over the entrance to the space ship and set out along the moonlit beach toward the nearest path running inland to his home. Men had no mates on Ortha, sex had been overthrown with all the other primitive impulses of barbarism; so he was incapable of understanding the emotions that swept through his acquired memory. Tonight or tomorrow night at the latest he must contact his two fellows and report that Earth was a planetary paradise. For three months he had lived with people who loved, hated, wept and sacrificed for reasons that he had never known existed.
 Though he wants it, he'll never truly belong. He'll always be an otherworlder.
 His Orthan background will always be at odds with his new life.  It's grueling to remember what he did to Terry, and to always have to be him now.  Though he wants it, he'll never truly belong. He'll always be an otherworlder.  He misses his life as an Orthan, even though he's come to enjoy Earth.