Think "the davinci code" for our national treasure, for example. but at the fbi laboratory in virginia, there's a small band of people whose real life job is to unlock encrypted communications. right now, they are stumped in an old murder investigation and they are asking for your help. here's cnn's jeanne meserve. >> reporter: in 1999 in this field near st. louis it, police found the body of ricky mccormick, unemployed, 41 years old. authorities think he was murdered. but why? by whom? two page afc notes written by mccormick and found in his pocket could hold key clues, but 12 years after the...