The search began on a cold spring day in 1986. Just after Ferdinand E. Marcos was ousted following two decades in power, volunteers working with the newly formed Filipino government entered an abandoned townhouse on East 66th Street in Manhattan.

It had been the residence where Imelda Marcos, the former president’s wife, often entertained guests, and the volunteers were looking for art — specifically, art they believed the couple had purchased using ill-gotten government funds.

But instead of paintings, they found only eight bronze nameplates identifying the art that they believed once hung on the now-empty walls. As the volunteers started piecing together a list of the paintings that had disappeared, those plaques — bearing names like Pablo Picasso, Vincent van Gogh, and Edgar Degas — became their first clues.

It was only the beginning of what has stretched into a decades-long hunt for the Marcoses’ art collection. Some works have turned up at auction and at residences of the Marcoses’ former associates, but only a small fraction of the collection, valued by the Filipino government at up to $500 million, has been recovered.