scene. in fact, a crime scene from the biggest art heist in history still unsolved. and this is all that's left. it is one of the art world's greatest mysteries. who stole these priceless works of art. and how have they managed to elude investigators all over the world for more than two decades. 13 works of art stolen, paintings by rembrandt, manet, flynk, sketches by degah. a chinese bronze beaker and a finial that set on top of a napoleonic flag. all taken in the dark of night. all together, worth $500 million. $500 million. and not one has ever been found. >> i'm randy kaye outside the isabella stewart gardener museum. this is where it all began march 18th, 1990.