Since the invasion into Ukraine began 11 months ago, investigators have opened more than 50,000 war crimes investigations looking at alleged atrocities committed by Russian troops. NPR Investigative Correspondent Tim Mak heard a rumor about a man, brutally killed, who lay in the streets of a town for 30 days. So he decided to investigate. One war crime, one story, to show the challenge that war crimes investigators face all over Ukraine.