When Martine Powers began looking into the mystery of the missing remains of Maurice Bishop, his cabinet members and supporters, one of the most noted explorations of the case turned out to be done by a group of high school boys in Grenada more than two decades ago. She was able to locate some of the nowadult investigators and the old principal of the school to learn what compelled them to do this as a class project, and how they found their sources.

One of the people they interviewed, a former Jamaican soldier, witnessed the exhumation at Calivigny. What he told them more than 20 years ago is central to why many Grenadians think the U.S. government has not told the entire story of what happened to the remains after they were discovered. But he eventually stopped responding to students.

Martine and her colleagues searched for the witness for more than a year. They also amassed hours of other tape from interviews with other people who were at the exhumation. What they were left with were incomplete memories of exactly what transpired the day the remains at Calivigny were recovered. Then, there was a breakthrough – with new questions about where all of this leads.

You can find photos and documents from the investigation in our special episode guide here: http://washingtonpost.com/emptygrave