As a young woman, documentary filmmaker Pamela Yates traveled to Guatemala to document the indigenous peasant revolution against the military government. She was granted incredible access to both the insurgents and the military, and the resulting interviews and footage became her 1984 film, When the Mountains Tremble. Twenty-five years later, she returns to her original footage to help make a legal case against the former Guatemalan dictator, to hold him accountable for genocide. Yates, forensic scientists, family members of the murdered, and a Spanish lawyer are all revealed as “granitos,” or grains of sand, contributing to the pursuit of justice.