so marinello watches and waits. >> we'd probably be the first ones to know about it.e do explore a lot of leads. we pass on those leads to law enforcement and let them run with it. >> investigator robert whitman says when it comes to stealing art, the actual theft is the easy part. once they have the goods, they need to know how to sell it without getting caught. >> that's the next step. and if they're going to sell it, it's like a car. it's not like that. the market for these artworks is very small. >> according to whitman, nearly all stolen, high-end artwork is eventually recovered. investigators continued with their search. chasing down countless tips and leads. then, in 1994, a possible breakthrough. that year, the museum director received a mysterious unsigned letter post stamped from new york. the anonymous writer said he had access to the stolen art and would barter them back for 1% of their value. >> the writer asked for two things. one was that the investigation stand down. what he meant by that was he was worried that those people who would facilitate -- hel