How could a man who stole one of the most famous paintings in the world still be a mystery more than 100 years later? It was the question that South Philly filmmakers Joe Medeiros and Justine Mestichelli Medeiros promised to answer after years of extensive research and interviews. They knew who did it. That was the easy part.

But the couple, who now lives in California, needed to unmask exactly why Italian immigrant Vincenzo Peruggia somehow walked out of the Louvre Museum in Paris in 1911 with the Mona Lisa and kept it hidden in his French apartment for two and a half years. It’s all detailed in an award-winning documentary called Mona Lisa is Missing that was shown at various festivals and private viewings, but it is finally set to air on public television on Aug. 28 at 6 p.m. on WHYY Philadelphia.