It was 2003, and Leora Krygier was rummaging around a thrift store near her home in Los Angeles. Krygier wasn’t looking for anything in particular, but a box of old vintage postcards caught her ...

A postcard mailed from the United Nations headquarters in New York arrived at the post office in Ottawa, Illinois, in August. It would have been unremarkable, except it had been postmarked at 8 p.m. — ...