Keth used to think that he was broken beyond anyone else's repair, but he hadn't counted on entering Khapik, where Yali healed his heart, Tris gave him back control over his body, and Dema gave him back his soul after his creations helped sentence innocent street-children to execution.
"If you want things to change," Dema told him, not unkindly, "then find a way to do it."
So after the others returned to the North, Keth stayed in Tharios and devoted his time to tracking killers. No more Glaki-like children, he resolved, would lose mothers; no more Yali-like women would lose their lives.
Sometimes he wondered if he was having too much fun, being paid to assist Dema's investigations, when yellow-clad singers still made him flinch. But Dema, who seemed to understand perfectly when it was acceptable to pat Keth's shoulder consolingly, would be there to focus on instead.
In the end, despite moments when they pressed too close while chasing criminals, breaths ragged, it was Keth who kissed Dema first. There was alcohol on his breath, but not enough to be blamed, so he instead assigned it to the truth: Keth could see his future in Dema's face and stride.