The story of the Gurlitt family, their deceptions and obvious awareness that their art trove was no legitimately theirs seems to have turned their son into a real life Gollum:

Speaking to Der Spiegel last week, during a trip to an unidentified German town to see a doctor for a heart condition, Mr. Gurlitt said he had not watched television since 1963 and had never gone online, but did talk to his pictures. He kept his favorites, a collection of works on paper, in a small suitcase that he would unpack each evening to admire.

Until the raid in February 2012, Mr. Gurlitt had guarded his privacy zealously, refusing to open his door even to meter readers from the gas company. He rarely spoke to or even acknowledged his neighbors. He had no friends whom anyone ever saw. […] The collection was so valuable and, perhaps, its provenance so tainted by the family’s association with the Nazis, that the desire to keep it secure compelled Mr. Gurlitt to live a strange, Gollum-like existence behind permanently drawn blinds, obscuring not only the works but also the man himself. […] “People only see banknotes between these papers with paint, unfortunately,” he said. […]

Konrad O. Bernheimer, a prominent Munich art dealer, said he had never come across Mr. Gurlitt despite decades in the business. “The saddest part of this whole story is this man’s life,” he said. “He was locked up in the dark with all these wonderful paintings. He is a man in the shadows, a ghost who never came out.”

For Son of a Nazi-Era Dealer, a Private Life Amid a Tainted Trove of Art – NYTimes.com.