It was a month into Vladimir Putin's invasion of Ukraine. Russian forces had withdrawn from around Kyiv and in their wake Bel Trew and her team stumbled on a body by an abandoned Russian camp. His hands were tied. He had been burned and shot in the back. Soldiers said he was a teenager. As Bel tried to find out who he was and what had happened, she uncovered a nightmare world: a nation struggling to find thousands of its missing and to identify its dead.