“Finding Oscar” is a magnificent journalistic collaboration documenting how prosecutors, forensic anthropologists and human rights activists persevered for 30 years in their quest for justice against the perpetrators of a 1982 massacre in Guatemala. The story begins with the compelling account of a 2011 phone call to Oscar Ramirez, an undocumented Guatemalan immigrant living in Massachusetts, from a prosecutor back home, informing him that he isn’t who he thinks he is. What follows, in both written and radio formats, takes us back in time to Dos Erres, a Guatemalan town whose 250 residents were killed by soldiers three decades ago. Oscar, it turns out, was one of two survivors, abducted at the age of three by the commander of the army squad that murdered his family, and he is now evidence of government complicity in the massacre. Recently several soldiers involved in the raid were convicted and the former Guatemalan President Efrain Rios Montt was indicted on charges of genocide.